- handling feelNot a vague, unpredictable feeling, but a comprehensive engineering index composed of control force, stop drift, rebound, response delay, terminal inertia and ergonomics, which can be quantified, compared and improved.
- Subjective descriptions can all correspond to physical quantities: "heavy" = the control force is too large, "frustration" = the starting force is too high/resistance fluctuations, "up/down" = aerodynamic balance pressure deviation, "rebound" = gas compressibility and terminal inertia, "unnatural switching" = pressure transition and response delay.
- Pneumatic balanced pressure regulation is key: Calculation examples show that a pressure deviation of only 0.02 MPa can generate approximately 37 N of additional control force - the pressure must be recorded simultaneously to evaluate the feel, rather than just subjective feedback.
- The evaluation method is based onPush-pull force gauge + pressure/displacement/angle sensor + response collection + subjective scoringCross-validation, supporting A-D classification, FMEA and "operating feel test record sheet", turns on-site "feeling" into traceable data.
Produced by: Jiangsu Aurek Intelligent Technology Co., Ltd. (AUREK Engineering Research Group) Document type: Technical information on engineering research and methods Version: V1.0 / 2026. This information is used for engineering research and method description.The formulas, calculation examples and sample data in this article are used to explain the analysis methods and evaluation ideas., the specific values are subject to actual measurement of the prototype, customer working conditions and safety requirements. The full text of the PDF can be downloaded at the end of the article or in the upper right corner.
00Abstract
Pneumatic Industrial Manipulator require operators to directly push, pull, position and release workpieces during processes such as handling, assembly, and loading and unloading. For a long time, their "operating feel" has been described by on-site personnel in subjective terms such as "light or not", "smooth or not", "whether there are frustrations", and "whether the stop is stable or not". This article believes that the operating feel is not simply a subjective feeling, but caused byControl force, starting force, uniform motion force, stop drift, rebound amount, response delay, joint damping, terminal inertia, tooling self-weight, compressed-air supply pressure stability, no-load/load pressure switching logic and ergonomic factorsThe jointly determined comprehensive performance can be transformed from subjective description into measurable and comparable engineering indicators.
Using the AUREK Pneumatic Industrial Manipulator engineering prototype ARK-S01 and site-commissioning experience, this article develops a handling-feel evaluation method for design, commissioning, and acceptance. Digital push-pull force gauges, pressure, displacement, and angle sensors, response-time acquisition, and operator ratings are combined to quantify handling feel at different loads, working radii, and tooling states. Mechanical models, representative calculations, test-record forms, and FMEA-based risk analysis explain the evaluation and diagnostic process. The stated parameters, calculations, and example data illustrate the method; conclusions must be verified by testing and adjusted using prototype measurements, customer operating conditions, and safety requirements. A single test must not be treated as evidence of full-life performance.
01Introduction
Pneumatic Industrial Manipulator are widely used in automotive parts, mechanical processing, box and plate handling, high-temperature workpiece transfer, assembly loading and unloading, etc. Different from simple lifting equipment, the Pneumatic Industrial Manipulator requires the operator to directly push, pull, position and release the workpiece during the operation. The equipment only assumes the "Remove gravity, keep control"Assisting effect. Because of this, the operating feel of the equipment will directly affect operating efficiency, positioning accuracy, operator fatigue, and on-site safety risks. In actual working conditions, the quality of the operating feel is often better than a single indicator such as the rated load to determine whether a piece of equipment is "easy to use."
On-site evaluations of the operating feel mostly appear in subjective terms, such as “it’s a bit heavy to push”, “there’s a hesitation when starting up”, “it will float up or sink down after letting go”, “it will rebound after stopping”, “no-load and load switching are not natural enough”, etc. These descriptions may seem subjective and vague, but they can all be mapped to specific, measurable physical quantities:
| Subjective description of the scene | Corresponding physical quantities/engineering causes |
|---|---|
| "Heavy/Can't push" | The control force is too large and the balance pressure is too low. |
| “Jerky startup” | Starting force is too high or running resistance fluctuates |
| "Floating/Sinking" | Pneumatic balance pressure deviation |
| "Rebound after stopping" | Gas compressibility and terminal inertia |
| "Switching is unnatural" | Unsmooth pressure transition and delayed response |
Table 1 Comparison of subjective feel description and engineering physical quantities
Therefore, converting subjective feel into engineering indicators is the prerequisite for achieving design optimization and quality consistency. This article focuses on the following questions: Can the operating feel be transformed from a subjective description into a quantifiable and reproducible engineering indicator? What mechanical, pneumatic, control and ergonomic factors will affect the operating feel, and what is the mechanism? How to use unified testing methods to evaluate the differences in feel between different machines, different fixtures and different load conditions? And how to feed the evaluation results back to cylinder selection, air path adjustment, fixture weight reduction, joint damping matching and operating armrest design?
02Engineering definition of research objects and operating feel
The research object of this article is a pneumatic balanced hard-arm Pneumatic Industrial Manipulator and its end tooling system. This type of equipment makes the workpiece in a "casual balance" state in space through the approximate balance of the cylinder output torque and the load torque. The operator only needs to apply a small force to complete the lifting, horizontal movement, positioning and release. The boundaries of the research object include the main boom, main, middle and front joints, pneumatic balance circuit, control valve group, operating armrest and end tooling, but do not include the fully automatic control system.
2.1 Engineering definition of operating feel
This article defines "operating feel" as: under the specified load, operating radius, stroke, compressed-air supply pressure and clamp status, the operator operates the armrest or clamp handle to make the Pneumatic Industrial Manipulator complete starting, lifting, horizontal movement, stopping, positioning, clamping and releasing, etc.Controlling force, response stability, motion continuity, stop holding ability and human comfortcomprehensive performance. This definition emphasizes four points: first, the feel is the performance under certain working conditions, and it is meaningless to talk about the feel without load, radius and pressure; second, the feel is the performance of the entire movement process, not a certain moment; third, the feel includes both mechanical quantities and ergonomic factors; fourth, the feel should ultimately be measured and evaluated.
2.2 Operation feel is a comprehensive indicator rather than a single indicator
The operating feel should not be described only as "light" or "not light", but should be broken down into multiple indicators such as mechanics, stability, response, dynamics and ergonomics, and supplemented by the operator's subjective evaluation for cross-validation. The engineering significance of each indicator is shown in the table below.
| Indicator category | Specific indicators | Engineering significance |
|---|---|---|
| Mechanical index | Starting force, uniform motion force, peak control force | Determine whether the equipment is labor-saving and whether it is stuck |
| stability index | Stop drift, rebound amount, pressure fluctuations | Determine the stability of positioning and maintenance |
| response metrics | Button response delay, pressure build-up time, action lag | Determine the sensitivity of the air path and control |
| Dynamic indicators | Terminal inertia, joint damping, motion overshoot | Determine whether the push-pull is fluttery or bulky |
| Ergonomics indicators | Armrest height, holding angle, button position, hand posture | Determine the fatigue level of long-term operation |
| subjective evaluation | Lightness, smoothness, stability, fatigue score | Correlation verification with objective data |
Table 2: Classification and engineering significance of operating feel indicators
03Analysis of factors affecting operating feel
The operating feel is formed by the superposition of multiple factors, and any one factor alone is not enough to explain on-site feedback. This article summarizes the main influencing factors asPneumatic balance, mechanical structure, fixture weight and terminal inertia, air circuit control and no-load/load switching, ergonomicsfive aspects.
3.1 Pneumatic-Balancing Factors
The Pneumatic Industrial Manipulator relies on the approximate balance between the cylinder output torque and the load torque to achieve power assistance. If the balance pressure is low, the operator needs to exert extra upward force, which is manifested as "sinking"; if the pressure is high, the equipment will tend to float upward, which is manifested as "floating upwards". Key factors affecting pneumatic balance include: whether the adjustment of no-load pressure and load pressure is reasonable, whether the compressed-air supply pressure is stable, the adjustment sensitivity of the pressure reducing valve, the friction and sealing resistance of the cylinder, and the buffering effect of the gas storage tank and one-way valve on pressure fluctuations. Among them,If the pressure transition is not smooth during no-load/load switching, it is easy to have a sudden upward or downward trend., making it a key focus of handling-feel evaluation.
3.2 Mechanical structural factors
The mechanical structure mainly affects starting resistance, running smoothness and stopping stability. The rotational resistance of the main joint, the middle joint and the front joint, the friction state of the bearings, pins, bushings and rollers, and whether there is drag on the joint brakes will all be directly reflected in the starting force and uniform speed control force. In addition, the stiffness of the main arm and the auxiliary arm, the gap between the connecting parts, changes in arm length, and changes in torque at different radius positions will also affect the size and consistency of the force felt by the operator at different positions. In actual working conditions, insufficient joint lubrication, bearing contamination or improper brake clearance are often the common reasons for "hard start-up and frustrated operation".
3.3 Tooling Self-Weight and End-Effector Inertia
Clamps are often an important source of impact on feel. Even if the manipulator body is well balanced, if the clamp is too heavy, the center of gravity is offset, or the inertia is too large, it will cause the end to sink, swing, rebound, or have difficulty in positioning. The design of custom tooling should not only focus on "whether the workpiece can be clamped", but should also pay attention to the fixture's self-weight, center of gravity position, total mass and moment of inertia after combination with the workpiece, as well as the different effects of different forms such as vacuum cups, gripper jaws, and air expansion shafts on the feel. For flipping fixtures, it is also necessary to calculate the changes in the center of gravity at different angles such as 0°, 45°, 90°, etc.; the drag of the air line, vacuum tube and cable will also change the force on the end during the horizontal movement and return process.
3.4 Air circuit control and no-load/load pressure switching factors
Air circuit control determines whether the action response is natural. The delay between the button triggering and the cylinder response, the matching of the valve group diameter and load, the tightness of the throttle valve adjustment, the length and bending of the pneumatic tubing, and the impact of moisture, oil and impurities in the compressed-air supply on the sensitivity of the valve will all change the operator's feeling of "following the hand".No-load/load pressure switching is the most sensitive link: If the pressure difference between loading and unloading is too large or the control logic is unreasonable, an instantaneous impact will occur, manifested as a sudden rise or sink at the moment of placing or picking up the piece. This article recommends setting up stress transition and verification logic for the switching process, and incorporating switching shock into response and stability testing.
3.5 Ergonomic factors
Even if the mechanical indicators are good and the armrest position and operating posture are unreasonable, the operator will still think that the equipment is "unusable". Whether the height of the armrest is close to the comfortable height of the operator's elbow, whether the buttons can be triggered in a natural holding posture, whether the lifting and clamping/release buttons are designed to prevent accidental touches, whether the two-hand operation complies with safety logic, whether the operating line of sight is blocked by fixtures or workpieces, and the fatigue caused by long-term repeated operations on the wrists and shoulders will all significantly affect the subjective evaluation. Therefore, ergonomic factors should be included in the evaluation alongside mechanical indicators, and the operator's height, arm span, and operating experience should be recorded during the test to explain the differences in scores between different personnel.
04Quantitative evaluation index system for operating feel
In order to convert the operating feel into measurable engineering indicators, this article establishes a set of quantitative evaluation index systems, which mainly include objective indicators such as control force, starting force and uniform motion force, stop drift and rebound amount, response delay and pressure fluctuation, as well as subjective scores associated with them. The symbols, units and recommended measurement tools of each indicator are summarized below.
| indicator | symbol | unit | Recommended measuring tools | Description |
|---|---|---|---|---|
| Starting force | Fstart | N | push-pull force gauge | Maximum operating force at start-up moment |
| uniform motion force | Fcv | N | push-pull force gauge | Average operating force in stable motion range |
| peak control force | Fpeak | N | push-pull force gauge | Maximum force during action cycle |
| Stop drifting | Dstop | mm | Displacement sensor/laser ranging | Displacement within specified time after letting go |
| rebound displacement | R | mm | Displacement Sensor/Video Analysis | Maximum reverse displacement after stopping |
| response delay | td | ms | data acquisition system | The time from button to action response |
| pressure fluctuations | ΔP | MPa | pressure sensor | Pressure changes during movement or switching |
| Equivalent inertia | Jeq | kg·m² | Calculation/Test Identification | Reflect end dynamic burden |
| joint damping | Bj | N·m·s/rad | Angle sensor + force test | Reflects the smoothness of horizontal rotation |
| subjective rating | Q | points | score sheet | Recommended 1–5 points or 1–10 points |
Table 3 Summary of quantitative indicators of operating feel
4.1 Control force and starting force
The control force is the most direct reflection of the operating feel, and refers to the push and pull force that the operator needs to exert on the armrest. A digital push-pull force meter is used to collect the change curve of the control force with time at the handrail's action point, and three types of characteristic values of starting force, uniform motion force and peak control force are extracted. Generally speaking, the smaller the control force and the smaller the fluctuation, the easier it is to carry and the better the feel. However, the control force should not be so small that it loses the "feel of control", otherwise it will easily cause drifting and positioning difficulties. The starting force reflects the static friction, brake drag, initial cylinder friction and load imbalance that the equipment needs to overcome from standstill to starting movement:
where Fstart is the starting force (N); F(t) is the time history of the control force; t0 is the moment when the operator starts to apply force; tv It is the moment when the terminal speed reaches the set threshold. When the starting force is high, the operator will obviously feel "failed to push down the first time" or "frustrated". The uniform motion force is defined as the average value of the absolute value of the control force within the stable speed range, and the force fluctuation coefficient is used to describe the stability:
where Fcv is the uniform speed control force (N); σF is the standard deviation of the control force in the uniform speed interval; CVF is the force fluctuation coefficient (dimensionless). Fcv The lower it is, the easier it is to carry it continuously; CVF The higher it is, the more likely it is that the operation will falter, crawl, or stall.
4.2 Stop drift and rebound amount
Stop drift measures the position change of the workpiece within a specified time after the operator lets go, reflecting the balance pressure, air tightness, braking state and load center of gravity stability; rebound amount measures the maximum reverse displacement that occurs in a short period of time after stopping:
where Dstop is the stop drift amount (mm), T is the observation time (can be 3 s, 5 s or 10 s and is fixed in the plan); R is the maximum rebound amount (mm). Excessive stop drift will affect the safety of positioning, assembly and placement; rebound is often related to gas compressibility, throttling settings, boom elasticity, fixture inertia and the operator's emergency stop action. If it is too large, the workpiece may hit the positioning surface or affect assembly accuracy. It is recommended to fix the observation time uniformly and record the drift and rebound at the same time to facilitate comparison between different models.
4.3 Correlation between response delay, pressure fluctuation and subjective ratings
Response latency measures the time between button triggering and action response, defined as td = tresponse − tbutton(ms). It is recommended to separately test the response delays of actions such as rising, falling, clamping, releasing, no-load switching, load switching, and load switching no-load. The pressure fluctuation ΔP is collected simultaneously by the pressure sensor. The subjective score is used to evaluate the ease of starting, smoothness of movement, stability of stopping, natural response, positioning comfort and operating fatigue from the operator's perspective. It is recommended to use a 1-5 point scale (5 is the best).Subjective scoring is not a replacement for objective testing, but is used to verify the correlation between objective indicators and operator experience; When the two show a stable correlation, it means that the evaluation system has good consistency.
05Mechanical models and calculation methods
In order to explain the causes of various indicators, this article gives several simplified mechanical models. These models are used to clarify the influence mechanism and magnitude relationship. Parameters such as efficiency, friction and inertia should be corrected in conjunction with actual measurements of the prototype during the project, and should not be used directly for accurate selection.
5.1 Cylinder output force and torque balance
The theoretical effective output force of the cylinder can be expressed as Fc = P·A·η, indicating that the output force is proportional to pressure, pressure area and overall efficiency. Taking the main rotation fulcrum as a reference, a simplified moment balance relationship can be established:
where Lc is the cylinder force arm (m); W is the total weight of the workpiece and fixture W=mg (N); Lw is the horizontal distance from the center of gravity of the load to the rotation fulcrum (m); Mf is joint friction resistance moment (N·m); Mi is the additional moment of dynamic inertia (N·m). This formula intuitively explains:Increased load, increased working radius, outward shift of the center of gravity of the fixture, or increased joint friction will all increase the required balancing pressure or control force.——This is the mechanical root of "the feel becomes worse when using large radius and heavy fixtures".
5.2 Control force and pressure deviation
The force felt by the operator at the handrail can be approximately obtained by dividing the combined value of the unbalanced moment, friction moment and inertia moment of the system by the equivalent force arm of the handrail: Fop = ΔM / Lh. If the air pressure deviation causes a moment imbalance, the additional control force caused by the pressure deviation is:
In the formula, ΔP is the pressure adjustment deviation (Pa); Lh It is the equivalent force arm (m) from the handrail's action point to the center of rotation. The above equation shows that the greater the pressure adjustment error and the shorter the armrest arm, the greater the push-pull force that the operator needs to compensate additionally. This explains why even a small pressure deviation may cause the operator to noticeably feel "floating" or "sinking".
5.3 Terminal equivalent inertia and comprehensive scoring model
The dynamic load at the end can be approximately described by the equivalent moment of inertia: Jeq = Jarm + Σ mi·ri². The heavier the clamp, the farther the center of gravity, the longer the arm, the higher the terminal inertia, which will lead to cumbersome starting, difficulty in stopping, and increased overshoot and rebound.Lightening the clamp and moving the center of gravity inward are important directions for improving dynamic feel.. On the basis of each sub-indicator, a comprehensive score of operating feel can be established for overall comparison of plans:
where SF、SD、SR、ST、SJ、SE They are control force, stop drift, rebound, response delay, joint smoothness and ergonomics score respectively; weight coefficient wi It is recommended to follow: safety-related indicators have a higher weight than comfort indicators; heavy-load conditions increase the weight of stop drift and rebound; precision assembly conditions increase the weight of positioning stability; high-frequency handling conditions increase the weight of control force and fatigue scores.
06Experimental plan and testing process
The test method proposed in this article aims to establish a set ofRepeatable, recordable and comparableThe operating feel evaluation process can be used for prototype commissioning, comparison of different fixture solutions, factory acceptance reference, customer on-site retesting, fault diagnosis and subsequent product optimization. It is recommended to configure a digital push-pull force gauge (with data output), 0–1.0 MPa pressure sensor, displacement sensor or laser rangefinder, angle encoder, data acquisition module with sampling rate not less than 50 Hz (response test not less than 100 Hz), auxiliary video and operator subjective rating form. Stopwatches can be used for preliminary testing, but formal studies recommend the use of a synchronous acquisition system to ensure the correspondence between force, pressure, displacement and time data.
In order to cover the typical usage range, this article recommends setting at least the following working conditions, covering no-load, different load proportions, different operating radius and load/no-load switching.
| Working condition number | Load status | Working Radius | height position | fixture status | Description |
|---|---|---|---|---|---|
| A1 | No load | minimum radius | median | Fixture no load | Measure basic resistance |
| A2 | No load | maximum radius | median | Fixture no load | Measuring the influence of arm span |
| B1 | Rated load 25% | middle radius | median | Normal gripping | Light load feel |
| B2 | Rated load 50% | middle radius | median | Normal gripping | Common working conditions |
| B3 | Rated load 75% | maximum radius | median | Normal gripping | Heavier working conditions |
| B4 | Close to rated load | maximum radius | high/low | Normal gripping | Extreme reference conditions |
| C1 | load shedding no load | middle radius | Placement | release action | Measuring switching shock |
| C2 | No-load-to-loaded transition | Pickup location | Pickup height | Gripping action | Test loading response |
Table 4: Design of operating feel test conditions
07Typical case analysis
To illustrate the application of the above model, this article gives a typical calculation example.The following calculation examples are only used to illustrate the method and are not used as a basis for selecting specific products., the actual parameters shall be subject to the actual measurement of the prototype and the design drawings.
7.1 Example conditions and equilibrium pressure calculation
Assume a certain handling condition: workpiece mass m1=80 kg, fixture mass m2=18 kg, total mass m=98 kg; distance L from the center of gravity of the load to the main fulcrumw=1.8 m; cylinder effective arm Lc=0.28 m; cylinder bore D=125 mm; cylinder comprehensive efficiency η=0.85; joint friction equivalent moment Mf=45 N·m. Calculate accordingly:
Under this assumption, the load balancing pressure is approximately 0.61 MPa, within the working range of common industrial compressed air. If the control force is obviously too large under the same load in the actual test, the possible reasons for the comparison model include: the center of gravity of the fixture is further outward than assumed, the joint friction torque is too large, the cylinder efficiency is lower than the estimated value, the compressed-air supply pressure fluctuates greatly, the no-load/load pressure is not adjusted to the appropriate state, or the armrest arm is too short. Most of these reasons can be investigated one by one through sub-tests, which embodies the idea of converting subjective feel problems into diagnosable engineering problems.
7.2 Effect of Pressure Deviation on Handling Feel
To illustrate the importance of pressure adjustment accuracy, assume the pressure adjustment deviation ΔP=0.02 MPa, the cylinder parameters are the same as above, and take the armrest equivalent force arm Lh=1.6 m, then the cylinder torque deviation and additional control force caused by the pressure deviation are:
Calculations show that even a pressure deviation of only 0.02 MPa may cause the operator toAn additional push and pull force of approximately 37 N was felt, enough to be clearly noticed as "floating" or "sinking". Therefore, pressure data must be recorded simultaneously in the evaluation of operating feel, rather than just the operator's subjective feedback.
08Test data record form and evaluation method
This section takes the example test performed by the AUREK Engineering Research Group on the engineering prototype ARK-S01 as an example to explain the data recording and evaluation methods. The following values are used to illustrate the methodSample data, only reflects typical trends. The specific results will vary depending on the prototype status, fixture, compressed-air supply and operator, and must be subject to on-site measurements. Each sample data is the representative value after 10 repetitions of each working condition.
8.1 Operating-Force Test
| Load/kg | Radius/mm | Air pressure/MPa | Starting force/N | Uniform force / N | Peak force/N | force fluctuation coefficient |
|---|---|---|---|---|---|---|
| 0 | 1800 | 0.50 | 21.8 | 11.5 | 27.4 | 0.08 |
| 40 | 1800 | 0.56 | 30.6 | 17.9 | 37.2 | 0.10 |
| 80 | 1800 | 0.61 | 38.4 | 22.6 | 46.1 | 0.12 |
| 80 | 2500 | 0.63 | 47.2 | 28.9 | 57.8 | 0.15 |
Table 5 Example data of control force test (prototype ARK-S01, fixture G01, operator OP-03, average of 10 repetitions)
It can be seen from the example data that both the starting force and the uniform force increase with the increase of the load and working radius, which is consistent with the moment balance model; under the large radius working condition (2500 mm), the force fluctuation coefficient increases from 0.12 to 0.15, indicating that the operation stability decreases, providing a quantitative basis for the "large radius feel deviation".
8.2 Stop drift, rebound and response delay
| Load/kg | Radius/mm | Height/mm | 5 s drift / mm | Maximum springback/mm | preliminary evaluation |
|---|---|---|---|---|---|
| 0 | 1800 | 1000 | 1.4 | 2.1 | Class A |
| 80 | 1800 | 1000 | 3.3 | 5.2 | Class A–B |
| 80 | 2500 | 1500 | 6.9 | 9.4 | Class B |
Table 6: Stop drift and rebound example data (5 s observation, prototype ARK-S01)
Stop drift and rebound increase as the load and radius increase, and the most unfavorable working conditions occur in large radius and high position states. Combining the effects of gas compressibility and terminal inertia, it is recommended to add buffer or speed-limiting designs to large inertia fixtures, and reduce rebound through throttle valve optimization. In the response delay test, the response from button triggering to the beginning of the displacement is about 119–224 ms, which is within the acceptable range of the operator; the response of the no-load/load switching action is the slowest and accompanied by a slight shock, which is consistent with the judgment in the third section that the switching link is the most sensitive. It is recommended to add pressure transition logic to the switching process.
8.3 Correlation between subjective ratings and objective data
| Evaluation items | Standard working condition (80 kg, 1800 mm) | Large radius working condition (80 kg, 2500 mm) |
|---|---|---|
| Startup ease | 4.3 | 3.4 |
| Smoothness of movement | 4.2 | 3.5 |
| stop stability | 4.4 | 3.3 |
| response naturalness | 4.1 | 3.6 |
| Positioning comfort | 4.2 | 3.2 |
| Operation fatigue | 4.0 | 3.1 |
Table 7 Comparison of subjective scoring examples (5-point scale, operator OP-03)
All subjective scores decreased significantly under the large radius working condition, which is consistent with the objective increase in control force, stop drift and rebound under this working condition. Correlation analysis of the sample data shows: load mass-starting force r≈0.97, operating radius-uniform control force r≈0.95, pressure fluctuation-stop drift r≈0.88, starting force-starting lightness score r≈−0.93, terminal inertia-stop overshoot r≈0.90.When objective indicators and subjective ratings show a stable and mechanism-based correlation, it means that the evaluation system is self-consistent., based on which the on-site "feel" can be transformed into trackable engineering indicators. The above correlation coefficients are illustrative results based on sample data, and the actual values need to be determined based on larger samples and on-site measurements.
8.4 Grading evaluation method
| level | Description | Applicable judgment |
|---|---|---|
| A | Easy operation, natural response, stable stopping | Can be used as optimization target |
| B | The operation is acceptable, a few indicators need fine-tuning | Can be used in general handling scenarios |
| C | Can complete the action, but there is obvious effort or drift | It is recommended to use after commissioning |
| D | Significant starting force, drift or impact | Direct delivery is not recommended and should be rectified |
Table 8: Recommendations for grading operating feel (recommendations from internal research of the company, not directly equivalent to industry standards)
09FMEA risk analysis
Operation feel issues are often intertwined with safety risks - stop drift, rebound, load switching shock and button mis-pressing not only affect the experience, but may also affect the safety of personnel, equipment and workpieces. The following table summarizes common feel-related failures in the form of Failure Mode and Effects Analysis (FMEA). The severity (S), occurrence (O), detection (D) and risk priority number (RPN=S×O×D) in the table are:Study example values, it needs to be corrected based on the actual failure data of the enterprise, frequency of on-site use and prototype test results.
| failure mode | Potential causes | Effect on handling feel and safety | S | O | D | RPN | Recommended actions |
|---|---|---|---|---|---|---|---|
| Starting force is too large | Insufficient joint lubrication, bearing contamination, and brake drag | Increased startup effort, frustration, and fatigue | 6 | 5 | 4 | 120 | Check joint resistance and optimize lubrication and braking clearances |
| Large fluctuations in uniform motion force | compressed-air supply pressure fluctuation, valve crawling, cylinder friction | Unsmooth movement and unstable positioning | 6 | 4 | 5 | 120 | Add pressure records and check pressure reducing valve and compressed-air supply quality |
| Float or sink after stopping | Improper adjustment of no-load/load pressure | Workpiece offset and safety risks | 8 | 4 | 4 | 128 | Establish pressure regulation standards and add stop drift testing |
| Excessive rebound when stopping | Large terminal inertia, too loose throttle, and boom elasticity | Collision when placing parts and incorrect assembly | 7 | 4 | 5 | 140 | Optimize throttling, reduce fixture inertia, and increase buffering |
| Response delay is obvious | The air hose is too long, the valve group diameter is insufficient, and the compressed-air supply is insufficient. | Operation lags and cycle time slows down | 5 | 5 | 4 | 100 | Optimize pipeline length and valve group specifications |
| No-load/load switching shock | The pressure difference is too large and the control logic is unreasonable | sudden rise or fall | 9 | 3 | 4 | 108 | Set up the switching verification process to optimize pressure transition |
| Excessive tooling self-weight | custom tooling have redundant structures and improper material selection | Feels bulky and has large inertia | 6 | 6 | 5 | 180 | the tooling is lightweight and the center of gravity is close to the connecting flange |
| air line or vacuum tube drag | Improper pipeline layout | The horizontal movement is too heavy and the return is unnatural. | 5 | 6 | 3 | 90 | Add drag chain/rotary joint to optimize pipe routing |
| The position of the armrest is unreasonable | Height, angle, distance do not match | Wrist and shoulder fatigue | 5 | 5 | 4 | 100 | Redesign the armrest position based on ergonomics |
| Button accidentally touched | Unclear button layout and no logic to prevent accidental touches | Fixture malfunction and safety risks | 9 | 2 | 4 | 72 | Double button release, button partition, added logo |
| The compressed-air supply contains water or impurities | Insufficient filtration and drainage | The response of the valve becomes slow and the action is unstable. | 6 | 5 | 4 | 120 | Increase filter-regulator inspections and establish a condensate-drain interval |
| Joint damping is too small | Insufficient damping design and large inertia | Horizontal rotation is fluttering and overshooting | 6 | 4 | 5 | 120 | Add adjustable damping or optimize damping matching |
Table 9: FMEA risk analysis related to operating feel (example, RPN is the company’s internal assessment model)
From the example RPN,The fixture's dead weight is too large (180), stop rebound is too large (140) and stop drift (128)The risks are relatively prominent and should be given priority during the design and debugging stages. FMEA is not only a risk list, but also a tool that matches hand feeling problems with improvement measures. It can be used in conjunction with the test record sheet to form a closed loop of "finding problems - quantifying problems - improvement verification".
10Optimization suggestions and engineering applications
Based on the above analysis, this article proposes optimization criteria from four aspects: pneumatic system, mechanical structure, fixture and ergonomics for design and debugging reference. The specific values and measures of each criterion still need to be determined based on prototype data and customer operating conditions.
| direction | Optimization criteria |
|---|---|
| Pneumatic system | Optimize the adjustment range and sensitivity of the pressure reducing valve and establish a pressure calibration process; rationally set up gas storage tanks and one-way valves to buffer pressure fluctuations; reduce air line pressure drop, optimize valve group diameter and load matching; add buffering and pressure transition logic for no-load/load switching. |
| Mechanical structure | Reduce joint friction, control joint clearance, and optimize the brake release state; increase boom stiffness to avoid long-term operation at the extreme position; perform damping matching for large radius working conditions to suppress drift and overshoot. |
| Tooling | Reduce the weight of the fixture and bring the center of gravity as close to the connecting flange as possible; reduce unnecessary overhanging structures and optimize the direction of the air line and vacuum tube; calculate the changes in the center of gravity at different angles for flipping fixtures; add buffering or speed-limiting designs to large inertia fixtures. |
| Ergonomics | The height of the armrest should be compatible with the height of the operator's elbow, and the holding angle should reduce wrist deflection; the buttons should be arranged in the natural reach area, and the release action should be designed to prevent accidental touches; high-frequency workstations should consider adapting to different heights; the operator's height, arm span, and operating experience should be recorded during the test. |
Table 10 Four-direction optimization criteria
This article recommends that in subsequent prototype development, on-site commissioning and customer acceptance,Uniformly use the "Operational Feel Test Record Form", gradually accumulating enterprise engineering databases under different loads, different fixtures and different working conditions. With the accumulation of data, the scoring weights, grading thresholds and FMEA parameters can be modified, so that the evaluation system gradually transitions from "empirical judgment" to "data-driven", providing a basis for design optimization and quality consistency.
11Conclusion
The following principal conclusions are drawn regarding the operating feel of the Pneumatic Industrial Manipulator:
(1) The operating feel is not a subjective, fuzzy, and unpredictable feeling, but is composed of control force, starting force, uniform motion force, stop drift, rebound amount, response delay, pressure stability, joint damping, terminal inertia and ergonomic factors.Comprehensive engineering indicators can be quantified and evaluated. (2) Push-pull force gauges, pressure sensors, displacement sensors, angle sensors, response time collection and subjective rating tables can together form a relatively complete evaluation system: objective testing identifies equipment status, and subjective ratings verify operator experience. The two corroborate each other. (3) Pneumatic balance pressure adjustment is a key factor affecting the feel; If the no-load and load pressures deviate from the reasonable range, it will cause floating, sinking, excessive starting force or stop drift. Therefore, it is recommended to record the pressure, load, radius and control force data simultaneously during prototype commissioning and delivery acceptance.
(4) The self-weight and terminal inertia of the fixture have a significant impact on the feel. The design of custom tooling should not only focus on whether the workpiece can be clamped, but also pay attention to the weight, center of gravity, inertia, and dynamic performance of the air hose drag and flip state. (5) Handling-feel evaluation should be combined with safety evaluation; Stop drift, rebound, load switching impact and button mis-pressing not only affect the experience, but may also affect the safety of personnel, equipment and workpieces. (6) It is recommended to establish a unified "operating feel test record form" and gradually form an enterprise engineering database so that the feel evaluation can move from experience to data.
12Reference test record appendix
To facilitate on-site use, this appendix provides a blank record sheet template for the operating feel test. Each unit can copy, expand and revise it according to the prototype and working conditions.
The subjective rating scale recommends using a 1–5-point scale (5 being the best), with clear anchor points: starting lightness (1=obviously laborious/3=acceptable/5=light and natural), movement smoothness (1=obvious stuck/3=occasional fluctuations/5=continuously smooth), stopping stability (1=obvious drift/3=slight drift/5=stop stable), response naturalness (1=obvious delay/3=acceptable/ 5=prompt response), positioning comfort (1=difficult to align/3=accomplishable/5=easy to position), operation fatigue (1=obvious fatigue/3=average/5=low fatigue). The complete blank record table (basic information table, control force table, drift and rebound table, response delay table, subjective rating table) can be found in the PDF full text appendix.