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Failure Mode and Effects Analysis Worksheet (Adapted from Cincinnati Machine PFMEA)Source{ www.ent.ohiou.edu/~me470/SnrDesign05_06/me471/FMEAWorksheet_SrD.xls
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Description of system and mode of operation Key Contact / Phone
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 Core Team:
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 Location:
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Potential Failure Modes and Hazard Identification Discussion: Identify all potential failures and safety hazards for this system in the applicable mode of operation. Complete a FMEA rating form for each significant item.
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FMEA rating form for a single Failure / Hazard
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Categorize:Action Results
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Identify susbsystem and modes of operationPotential Failure Mode and whysPotential Effect(s) of FailureS
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V		Probability of Occurrence of Failure O
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C		Current
Process
Controls		D
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T		R
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N		Recommended Action(s)Action TakensS
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V		O
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Wheelchair Control
in VR		Control failure
(Sensor malfunction)		Users cannot control the virtual wheelchair in VR environment10Sensor malfunctions are relatively rare but may occur after prolonged use or equipment damage.3Regular hardware quality checks254Use high-quality sensors
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Delayed response
( Computational delay)		Causing an unrealistic experience and making it hard to sync movements with the virtual environment.8Modern computers and VR devices typically have enough processing power to minimize delay.2Regular testing and optimization of system performance.116Optimize software algorithms
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Inaccurate speed tracking
(Inaccurate rotational speed tracking device)		Inconsistent movement performance, making skill learning difficult8This issue occurs moderately due to sensor precision problems.4Calibration of sensors and use of precision tracking devices.396Regularly calibrate rotational sensorsAdd calibrate process before training.53345
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Glitches in the VR software cause the system to freeze or crash.Users may lose confidence in the system and abandon it.4The system may have an unfixed bug.4Regular update system for stablility.348Optimize software algorithm
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Sudden loss of power disrupts the VR experience.Interrupt the training.4The issue occurs due to the power supplier's loss or not appropriate position of power supply.1Check power supplyer before use28Make sure the power supplyer is working.
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Racket Control in VRInaccurate or delayed racket movement
(Inaccurate hand tracking)		User cannot hit the ball accurately, impacting training results8Hand tracking accuracy issues occur at a moderate frequency, especially with low-quality devices. 4Regular testing of hand-tracking devices and software updates.264Improve hand-tracking algorithms, use advanced sensors
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Failure to simulate realistic racket-ball interaction
(Defects in physics engine or feedback system)		Unable to experience realistic ball-hitting sensations, reducing effectiveness7The physics engine is usually mature, and such failures are rare.2 Continuous optimization and debugging256Enhance feedback systems, and perform extensive user testing.That's why we are trying to add a haptic feedback system2228
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Uncomfortable racket
(Wrong materials/shapes)		leading to sharp edges might injure the user9If ergonomic materials and shapes are used during the design phase, this issue is unlikely to occur.1Ergonomic design testing and material selection.19Use soft, rounded materials and thoroughly test for comfort before production.We have already started testing prototypes with flexible fabrics and ergonomic designs.3113
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Straining the User’s Hand
(Overuse or High Loads)		Users may experience hand fatigue, soreness, or even injury, which can cause discomfort and limit training duration.7Users will feel tired after using the vr controller for more than an hour4Implementing usage time limits and providing ergonomic devices.256Provide regular breaks, use ergonomic designs, and limit usage time to avoid fatigue.
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Sensor inaccuracies in the racket handle Missed hits or inaccurate feedback.5Inaccurate position of the sensor or manufacturer defect during the assembly process.4Real-time swing calibration algorithms.360Conduct motion-capture studies to refine racket swing detection.Added backup sensors for motion detection.52330
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Connectivity issues between racket and VR system.Reduced user engagement and effectiveness.4Connection get disturbance.4Regular system updates.348Add diagnostics for connectivity or motion errors.
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Racket hit on wall during training.Break the device or injury hand.9No enough distance from the wall.2Set up warning in the system.9162Add reminders and warnings in the system and before training.Add a check feature before training and device setup procedure.92118
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Mechinical structureTransmission devices jammed or malfunction
(Improper design of transmission devices)		The wheelchair, racket control systems, etc., cannot operate smoothly, possibly causing training interruptions or equipment damage.9This issue can occur due to design flaws or material issues, with moderate frequency.3Regular inspections and testing of transmission devices. 372Use durable materials, implement regular maintenance checks, and perform system diagnostics.Add an inspection method for the user.63354
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Loose connections in the transmission system and control mechanisms
The equipment may become loose or break, affecting the stability and safety of the system.8Loose connections are usually caused by poor design or improper assembly4Design optimization and quality control during assembly.372Improve design, use higher-quality connectors, and implement stricter quality control during assembly.
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Equipment Failure
(Poor Insulation or Moisture Ingress)		Could make the device non-functional8Proper protective design and moisture-proof treatment usually prevent such issues. 2Proper insulation design and moisture protection.232Ensure effective sealing, improve insulation, and perform regular maintenance checks for moisture protection.
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Insufficient Cooling
(Overheating of Components)
The user may experience physical discomfort, such as the sensation of heat or minor burns from prolonged contact with an overheated device.7Inadequate cooling design or prolonged high-load use may lead to overheating.3 Improved cooling system design and heat dissipation management.363 Improve cooling systems, increase ventilation, and use heat-resistant materials.
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Structural failure under dynamic motion (e.g., wheelchair movement).Safety risks for users, the user may fall down during training, which can cause injury to the user.9inappropriate assemble before use.3Stress-testing mechanical components.5135Perform rigorous load testing on critical components.Added shock absorbers to reduce stress on critical points.32424
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Inadequate durability for repeated stress cycles.Disruption to training sessions.7Device overload or use more than the design capacity.3Use of durable, lightweight materials.484Develop a maintenance checklist for users.Updated design to comply with safety standards.22416
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Haptic feedbackInaccurate or non-functional feedback
(Coding Errors or Frequent Updates)		User cannot perceive important tactile feedback, reducing training effectiveness6Coding errors or updates are usually solvable through debugging, making this issue rare.2Software testing and frequent updates to ensure accuracy.224Regularly test and update software, improve coding practices, and use automated testing tools.
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Feedback too strong or falseUser discomfort due to excessive feedback, affecting training comfort7Feedback issues may occur when the settings are not properly adjusted.4User feedback collection and adjustment of feedback settings.384Adjust feedback intensity settings, use adjustable feedback systems, and gather user feedback regularly.Using prototype to test it for now53230
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Overheating of haptic components.
There are safety risks for users because the haptic device is wearable, so it is closer to the user's skin and can cause minor burns.
9inappropriate cooling design.2Thermal monitoring of haptic components.6108Ensure thermal management systems are in place.Limit electric motor power.22624
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Lag in haptic response due to processing delays.Potential for user frustration.6software bug.2Use of efficient algorithms to reduce latency.336Conduct usability testing to refine haptic responses.
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1. Discuss root cause of the failure mode (based on the 5 whys)
Mechanical Structure - Material Yield
Root Cause: Prioritization of cost and weight over durability, leading to the selection of materials that may not withstand operational stresses.
Actuation System - Wear or Loose
Root Cause: Design emphasis on user convenience and minimal maintenance, without providing clear instructions or reinforcement for routine upkeep.
Sensing Components - Thermal Shock
Root Cause: Lack of clear guidance on safe operating conditions, leading to use in uncontrolled environments and exposure to sudden temperature changes.
Control Electronics - Electrical Short
Root Cause: Insufficient sealing or insulation in design to keep costs low, resulting in vulnerability to moisture or contaminants.
Software Interface - Software Bug
Root Cause: Limited resources and time for thorough testing, due to reliance on open-source or educational project funding, leading to potential bugs in software updates.
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2. Discuss/justify the severity rating (SEV)
Material Yield-posing a hazardous situation without warning.
Wear or loose-hazardous situation without warning.
Thermal Shock-burns without warning.
Electrical Short-major loss of primary function.
Software Bug- reduce secondary function performance
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3. Discuss/justify the rating for probability of occurrence (OCC)
Wrong Material Selection (OCC: 1)-Provided that standard protocols are followed, the chances of choosing an incorrect material are low.
Overuse or High Loads (OCC: 5)-possible that users may unintentionally subject the device to loads beyond its intended capacity.
Insufficient Cooling (OCC: 2)-overheating can be avoided if the device is used within recommended operating conditions.
Poor Insulation or Moisture Ingress (OCC: 2)-Proper insulation and environmental protection are standard practices.
Coding Errors or Frequent Updates (OCC: 5)-Coding errors or issues from frequent updates are rated as moderate.

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4. Discuss/justify the rating for the probability of detecting a "failure imminent" condition and avoiding the failure (DET)
The Probability of Detection (DET) rating is key to evaluating whether a failure can be detected before it causes significant consequences, or whether corrective actions can be taken to prevent the failure.
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5. Recommended actions: Make specific recommendations for action and include some discussion of the alternatives that were considered.
The possible actions mainly focus on improving hardware quality, optimizing software algorithms, regular calibration and maintenance, improving design and materials, and enhancing user comfort.
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6. Notes on Actions taken:
We are utilizing our prototype to test and validate high-priority failure modes through various methods, aiming to identify and mitigate potential issues effectively. This process is focused on reducing the Risk Priority Number (RPN) and enhancing the overall reliability of the system.
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