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After completing the actuator assembly, the module must be tested to verify proper operation and determine the correct motor phase sequence for the motor driver.

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Overview

Actuator testing involves:
  • Mechanical verification of assembly quality
  • Encoder signal verification
  • Motor phase sequence determination
  • Current draw verification
  • Thermal performance testing
  • Final quality check
Safety First
  • Never connect power without proper current limiting
  • Do not exceed rated voltage (typically 24V for these actuators)
  • Monitor temperature during testing - the motor should not exceed 80°C
  • Keep fingers away from moving parts during powered operation
  • Have emergency stop readily available

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Required Equipment

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Test Equipment

  • Motor driver board (micro driver or compatible)
  • Power supply (24V, minimum 5A capacity)
  • Multimeter
  • Oscilloscope (optional, for encoder signal verification)
  • IR thermometer or thermal camera
  • Test stand or fixture to hold actuator

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Connections

  • Motor phase cable (3 wires)
  • Encoder cable (5 wires: +5V, GND, A, B, Index)
  • Power supply cables

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Pre-Test Mechanical Verification

Before applying power, perform these mechanical checks:
1

Check free rotation

Manually rotate the output shaft through its full range:
  • Rotation should be smooth throughout
  • No binding or tight spots
  • No unusual noise or grinding
  • Resistance should feel even
If you feel binding, do NOT apply power. Disassemble and check for:
  • Timing belt teeth not engaged properly
  • Bearings not seated correctly
  • Codewheel touching encoder
  • Rotor rubbing on stator
2

Inspect for clearances

Visually inspect:
  • Codewheel has clearance from encoder (0.5-1mm gap)
  • Timing belts are centered on pulleys
  • No wires pinched between shell halves
  • All fasteners are secure
3

Check encoder mounting

Verify:
  • Encoder screws are tight
  • Encoder body is not touching codewheel
  • Encoder connector is secure

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Encoder Signal Verification

1

Apply encoder power

Connect encoder power:
  • +5V to encoder power pin (typically red wire)
  • GND to encoder ground pin (typically black wire)
Use a current-limited power supply set to 50mA maximum. A properly functioning encoder draws 15-30mA.
2

Verify power consumption

Measure encoder current draw. Typical values:
  • Normal: 15-30mA
  • Short circuit: >50mA (indicates wiring problem)
  • Open circuit: less than 5mA (indicates poor connection)
3

Check encoder signals with multimeter

With encoder powered, slowly rotate the output shaft and measure:
  • Channel A: Should toggle between 0V and 5V
  • Channel B: Should toggle between 0V and 5V (90° phase shift from A)
  • Index: Should pulse once per revolution
If signals don’t toggle:
  • Check wiring connections
  • Verify encoder is powered
  • Check codewheel is rotating (watch through encoder gap)
  • Inspect codewheel for damage or contamination
4

(Optional) Oscilloscope verification

For detailed signal quality verification:
  1. Connect oscilloscope to Channel A and Channel B
  2. Rotate output shaft at moderate speed
  3. Verify:
    • Clean square wave signals
    • 90° phase relationship between A and B
    • Signal voltage swings rail-to-rail (0V to 5V)
    • No excessive noise or ringing

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Motor Phase Sequence Determination

The correct motor phase sequence must be determined for proper motor operation with the driver.
1

Initial motor connection

Connect motor phase wires to driver in arbitrary order. Label them as A, B, C (or U, V, W depending on driver convention).
2

Apply low current test

Set motor driver to:
  • Current limit: 0.5A (low current for safety)
  • Velocity: Very slow rotation (e.g., 1 rad/s)
  • Position control mode (if available)
Apply power and command slow rotation.
3

Observe motor behavior

Correct phase sequence: Motor rotates smoothly in commanded direction.Incorrect phase sequence: Motor will exhibit one of these behaviors:
  • Stuttering or cogging
  • Rotating in wrong direction
  • Not rotating at all (vibrating/humming)
  • Excessive current draw
4

If phase sequence is incorrect

If motor doesn’t rotate smoothly:
  1. Disconnect power
  2. Swap two motor phase wires (e.g., swap B and C)
  3. Retest
  4. If still incorrect, try a different pair
There are 6 possible phase combinations:
  • ABC, ACB, BAC, BCA, CAB, CBA
Only one will produce smooth rotation in the correct direction.
Systematic approach: Start with ABC. If wrong, try ACB. If still wrong, try BAC. Continue until correct sequence is found.
5

Verify direction

Once smooth rotation is achieved:
  1. Command positive velocity
  2. Verify output shaft rotates in expected direction
  3. Check encoder count increases in expected direction
If direction is wrong but operation is smooth, simply reverse two phases.
6

Document phase sequence

Label the motor phase wires permanently with the correct sequence for your driver. Many teams use colored heat shrink or labels.

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Performance Testing

1

Increase current gradually

With correct phase sequence established:
  1. Increase current limit to 1A
  2. Command slow rotation and verify smooth operation
  3. Gradually increase to 2A, 3A, etc.
  4. Test up to rated current (typically 8-12A for these actuators)
Monitor motor temperature continuously during current testing. If motor exceeds 80°C, reduce current or allow cooling time.
2

Test velocity range

Test motor at various speeds:
  • Very slow (0.1 rad/s) - verify no cogging
  • Medium (5 rad/s) - typical operation speed
  • Fast (20+ rad/s) - verify no vibration
Note any unusual behavior at specific speeds.
3

Test position control

If using position control:
  1. Command step changes in position
  2. Verify actuator reaches commanded position
  3. Check for overshoot or oscillation
  4. Verify encoder count matches commanded position
4

Current draw verification

Measure current draw during operation:
  • No load: less than 0.5A at moderate speed
  • Light load: 1-3A typical
  • Heavy load: Up to rated current
Excessively high current with no load indicates:
  • Mechanical binding
  • Incorrect phase sequence
  • Damaged motor windings
5

Thermal testing

Run actuator at typical operating current for 10-15 minutes:
  1. Measure motor case temperature every 2 minutes
  2. Temperature should stabilize below 80°C
  3. If temperature exceeds 80°C, reduce duty cycle or improve cooling
Typical temperatures: At 3A continuous current, motor case temperature typically reaches 50-60°C at ambient temperature of 20-25°C.
6

Noise and vibration check

During operation:
  • Listen for unusual noises (grinding, clicking, squealing)
  • Feel for excessive vibration
  • Check that timing belts remain centered on pulleys
Unusual noise or vibration may indicate:
  • Timing belt teeth skipping
  • Bearing damage
  • Loose fasteners
  • Rotor/stator rubbing

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Final Quality Check

After testing, perform final inspection:
1

Power-off inspection

Disconnect power and check:
  • All fasteners remain tight
  • No visible wear on timing belts
  • Timing belts still centered on pulleys
  • No signs of overheating (discolored plastics, melted insulation)
2

Free rotation check

Manually rotate output shaft:
  • Should still feel smooth (not worse than before testing)
  • No new noises or binding
3

Documentation

Record for future reference:
  • Correct motor phase sequence (wire colors and driver connections)
  • Encoder channel assignment
  • Serial number or build date (label on actuator)
  • Any notes about assembly or testing

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Acceptance Criteria

An actuator passes testing if: ✓ Motor rotates smoothly with no binding throughout full range
✓ Encoder signals are clean and toggle correctly
✓ Correct motor phase sequence has been determined
✓ Current draw is within expected range (less than 0.5A no load at moderate speed)
✓ Temperature remains below 80°C at rated current
✓ No unusual noise or vibration during operation
✓ Position control (if applicable) accurately tracks commands
✓ All mechanical fasteners remain secure after testing

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Troubleshooting

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Motor won’t rotate

  • Verify motor driver is powered and enabled
  • Check motor phase connections
  • Verify current limit is not set too low
  • Check for mechanical binding

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Encoder not working

  • Verify encoder power supply (5V)
  • Check encoder wiring and connector
  • Verify codewheel is not touching encoder
  • Inspect codewheel for damage or contamination
  • Check codewheel is rotating with motor shaft

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Excessive current draw

  • Check for mechanical binding
  • Verify motor phase sequence is correct
  • Check for damaged motor windings (measure phase resistance)
  • Verify timing belts are not over-tensioned

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Overheating

  • Reduce duty cycle
  • Improve cooling (airflow)
  • Verify current limit is appropriate
  • Check for mechanical losses (binding, belt friction)

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Encoder position drifts

  • Codewheel may be wobbling (check bonding alignment)
  • Encoder gap may be too large (>1mm)
  • Electrical noise interference (check grounding and shielding)
  • Check index pulse is occurring once per revolution

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Next Steps

With testing complete, your actuator is ready for integration:
  • Install actuator in robot assembly
  • Configure motor driver parameters
  • Implement control algorithms
  • Perform system-level testing

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