Troubleshooting Guide

Power Issues

Power System Troubleshooting

Complete Power Loss

Symptoms: No robot response, no LED indicators, complete electrical silence

Diagnosis Steps:

1. Battery Voltage Check

   Expected: >11.5V under no load
   Tools: Digital multimeter
   Test Points: Battery terminals
   Red Flag: <11.0V indicates battery failure

2. Main Breaker Verification

   Check: Physical position (ON/OFF)
   Test: Continuity across breaker
   Look For: Visible damage, burning, corrosion
   Action: Cycle breaker if necessary

3. SB Connector Inspection

   Visual: Connector engagement and condition
   Physical: Push/pull test for security
   Electrical: Voltage at robot side of connector
   Clean: Remove oxidation/corrosion if present

Partial Power Loss

Symptoms: Some systems work, others don’t, intermittent operation

Isolation Strategy:

Step 1: Identify affected circuits
Step 2: Check individual fuses/breakers
Step 3: Measure voltage at load end
Step 4: Check connection security
Step 5: Measure current draw

Common Causes & Solutions:

• Blown Fuse: Replace with same rating, investigate cause
• Loose Connection: Re-torque to specification, apply thread locker
• Wire Damage: Inspect for pinch points, chafing, cuts
• Overload: Check current draw, compare to fuse rating

Brownout Conditions

Symptoms: Intermittent resets, performance degradation, voltage warnings

Investigation Process:

1. Battery Load Test

   • Apply 200A load for 10 seconds
   • Voltage should remain above 10.5V
   • If fails, replace battery immediately

2. Connection Resistance Check

   • Measure voltage drop under load
   • Should be less than 0.5V total from battery to PDH
   • Clean and retorque high-resistance connections

3. Load Analysis

   • Monitor current draw during operation
   • Compare to fuse ratings and wire capacity
   • Identify unexpectedly high current draws

Communication Failures

Communication System Troubleshooting

CAN Bus Failures

Symptoms: Devices not responding, intermittent communication, error messages

Physical Layer Diagnostics:

Test 1: CAN-H and CAN-L Continuity
Expected: Continuous path from end to end
Tools: Multimeter in continuity mode

Test 2: Bus Termination
Expected: 60Ω ±5% between CAN-H and CAN-L
Tools: Multimeter in resistance mode
Note: All devices disconnected for accurate reading

Test 3: Ground Continuity  
Expected: <1Ω between all device grounds
Tools: Multimeter in resistance mode

Network Layer Issues:

• Device ID Conflicts: Use diagnostic tool to scan for duplicates
• Baud Rate Mismatch: Verify all devices configured for same rate
• Message Timing: Check for excessive bus loading

Application Layer Problems:

• Firmware Compatibility: Ensure all devices have compatible versions
• Parameter Conflicts: Review configuration for conflicting settings
• Error Recovery: Check device error logs and recovery mechanisms

Ethernet Network Issues

Symptoms: Vision system offline, driver station disconnects, network timeouts

Cable Testing Procedure:

Physical Inspection:
- Check connector engagement
- Look for cable damage or stress
- Verify proper strain relief

Electrical Testing:
- Use cable tester for wire map
- Check for opens/shorts/miswires
- Verify proper T-568B termination

Network Testing:
- Ping test for basic connectivity
- Bandwidth test for performance
- Packet loss measurement under load

Radio Communication Problems

Symptoms: Driver station disconnects, poor signal strength, intermittent control

Systematic Approach:

1. Power Supply Check: 12V ±10% at radio
2. Ethernet Connection: Cable integrity and connection
3. Antenna System: Connection security and orientation
4. Network Configuration: IP settings and subnet mask
5. Environmental Factors: Interference sources, physical obstructions

Motor Control Problems

Motor Control Troubleshooting

Motor Non-Responsive

Symptoms: Motor doesn’t move despite commands, no current draw

Power Path Verification:

Step 1: PDH Output Voltage
Measure: Voltage at PDH terminals under load
Expected: 12V ±10%

Step 2: Controller Input Voltage  
Measure: Voltage at motor controller power input
Expected: Same as PDH output ±0.5V

Step 3: Motor Power Connections
Check: All power connections secure
Look For: Burned contacts, loose connections

Step 4: Fuse Continuity
Test: Fuse/breaker continuity
Replace: If open circuit detected

Control Signal Verification:

CAN Communication:
- Device visible on CAN bus
- Responds to configuration commands
- No error flags in device status

Control Mode:
- Verify correct control mode selected
- Check command value ranges
- Confirm enable/disable state

Erratic Motor Behavior

Symptoms: Unexpected movements, oscillation, poor performance

Feedback System Check:

• Encoder Connections: Verify all encoder wires secure
• Signal Quality: Check for noise or intermittent signals
• Mechanical Coupling: Ensure encoder properly coupled to motor
• Software Configuration: Verify encoder resolution and direction

Control Loop Analysis:

• Gain Settings: Check P, I, D values for stability
• Setpoint Limits: Verify command values within reasonable range
• Feed Forward: Ensure FF terms appropriate for mechanism
• Current Limiting: Check if current limits causing issues

Motor Overheating

Symptoms: Excessive motor temperature, thermal shutdowns, performance degradation

Investigation Steps:

1. Current Draw Analysis

   • Measure actual vs. expected current
   • Compare to motor specifications
   • Check for mechanical binding

2. Thermal Management

   • Verify adequate ventilation
   • Check for blocked cooling paths
   • Monitor ambient temperature effects

3. Duty Cycle Evaluation

   • Assess actual vs. rated duty cycle
   • Consider peak vs. continuous ratings
   • Implement current limiting if necessary

Sensor Issues

Sensor System Troubleshooting

Encoder Issues

Symptoms: Position feedback errors, velocity calculations incorrect, robot drift

Signal Integrity Check:

Power Supply:
- Verify 5V ±0.25V at encoder
- Check current draw within specifications
- Look for power supply noise/ripple

Signal Quality:
- A/B channel signals clean and square
- Proper signal levels (0V/5V for digital)
- Phase relationship correct (90° apart)

Mechanical System:
- Coupling secure and aligned
- No mechanical play or backlash
- Proper mounting and strain relief

Common Encoder Problems:

• Wire Damage: Check for pinched or cut wires
• Connector Issues: Verify proper engagement and contact
• EMI Interference: Route away from high-current wires
• Power Issues: Ensure clean, stable power supply

Limit Switch Failures

Symptoms: Overtravel, mechanism damage, inconsistent triggering

Testing Procedure:

Electrical Test:
1. Measure resistance: Open/Closed states
2. Check actuator travel and force
3. Verify wiring continuity
4. Test under vibration conditions

Mechanical Test:
1. Actuator alignment and engagement
2. Mounting security and positioning
3. Repeatability of switching point
4. Force required for activation

Vision System Issues

Symptoms: Target detection failures, processing delays, network timeouts

Systematic Diagnosis:

1. Physical System

   • Lens cleanliness and focus
   • Lighting conditions and consistency
   • Target visibility and contrast
   • Camera mounting and stability

2. Network Performance

   • Ethernet connection integrity
   • Network bandwidth utilization
   • Processing latency measurement
   • Packet loss under load conditions

3. Software Configuration

   • Pipeline settings and thresholds
   • Target detection parameters
   • Network table updates and timing
   • Error logging and diagnostics

Power Emergencies

Power System Emergency Repairs

Battery Connection Failure

Quick Fix Options:

Option 1: SB Connector Cleaning
- Disconnect battery immediately
- Clean contacts with fine sandpaper/emery cloth
- Apply contact cleaner if available
- Reassemble with firm engagement

Option 2: Bypass Connection
- Use jumper cables with ring terminals
- Connect directly to breaker terminals
- Secure cables to prevent shorts
- Label as temporary repair

Option 3: Connector Replacement
- Cut damaged connector from wire
- Strip wire and install ring terminals
- Connect directly to breaker or PDH
- Insulate connection thoroughly

Fuse/Breaker Failure

Immediate Actions:

Step 1: Identify Failed Protection
- Visual inspection for blown fuse
- Continuity test if time permits
- Check for signs of overheating

Step 2: Replace Protection Device
- Use identical rating replacement
- If unavailable, temporarily use next lower rating
- Document temporary change

Step 3: Address Root Cause
- Check for short circuits
- Verify load current within limits
- Inspect wiring for damage

PDH Emergency Issues

Critical Procedures:

• Total PDH Failure: Bypass with fused connections directly from battery
• Individual Channel Failure: Redistribute loads to working channels
• Communication Loss: Switch to PWM control if CAN fails

Connection Failures

Connection Emergency Repairs

Connector Damage

Field Repair Techniques:

Powerpole Connector:
1. Cut damaged connector completely off
2. Strip wire to appropriate length
3. Install ring terminal with crimper
4. Connect directly to device terminal
5. Insulate with electrical tape/heat shrink

Molex SL Connector:
1. Cut individual damaged wires
2. Strip and tin wire ends
3. Use small wire nuts for connections
4. Insulate each connection separately
5. Bundle and secure against strain

Ethernet Connector:
1. Cut cable beyond damage point
2. Install new RJ45 connector
3. Verify T-568B wiring standard
4. Test with cable tester if available

Wire Damage Repairs

Priority-Based Approach:

Critical Circuits (Power, Safety):
- Solder splice with heat shrink
- Multiple wrapping layers for insulation
- Mechanical strain relief
- Test under load before use

Important Circuits (Control, Communication):
- Twist splice with mechanical connection
- Electrical tape insulation minimum
- Protect from moisture and vibration
- Monitor for degradation

Non-Critical Circuits:
- Temporary twist connection acceptable
- Basic insulation required
- Plan permanent repair after competition

Quick Bypasses

Emergency Bypass Procedures

CAN Bus Failures

Bypass Strategies:

Option 1: PWM Fallback
- Reconfigure motor controllers for PWM control
- Use RoboRIO PWM outputs
- Limited functionality but operational
- Monitor for overheating without CAN feedback

Option 2: Parallel CAN Bus
- Run temporary CAN wires
- Use existing spare conductors
- Maintain proper termination
- Test communication before enabling

Option 3: Device Isolation
- Disconnect failed device from bus
- Maintain termination integrity
- Operate with reduced functionality
- Document disabled systems

Vision System Bypass

Alternative Approaches:

Manual Control Mode:
- Disable autonomous vision dependency
- Rely on driver skill and practice
- Use backup sensors for reference
- Communicate limitations to drive team

Simplified Vision:
- Reduce processing complexity
- Lower resolution/frame rate
- Basic target detection only
- Accept reduced accuracy for reliability

Communication Failures

Redundancy Activation:

Radio Backup:
- Secondary radio configuration
- Alternative network path
- Reduced bandwidth operation
- Critical control only

Ethernet Redundancy:
- Backup cable routing
- Alternative switch ports
- Point-to-point connections
- Reduced network functionality