Hydraulic power steering tests:
- assembly preconditioning
initialization of the rack and pinion assembly to break in the internal components
- purge cycle
repeated cycling of the input shaft to bleed any air out of the test fluid
- end-stop calibration
determination of end-stop positions (maximum travel) and the center position of the rack
- fluid temperature
repetition of any subsequent test at a different, closed-loop control temperature
- idle torque
measure the required torque to move the rack with no test fluid back-pressure
- steer torque detector response
measure the required time to move the full stroke of the rack based on a predefined input torque
- total angle of rotation
measure the total angle on each side from the center-point that the input shaft can be rotated
- boost curve
measurement of the test fluid pressure vs. input torque when the rack is locked
- performance test
measurement of the input shaft applied torque that is needed to overcome a predefined static force at the rack
- force characteristic
measurement of input torque when a specific force is applied to the rack end
- drift & backlash
measurement of the rack drift, stiffness, and backlash at the center position
- steering sensitivity
measurement of the torsion coefficient of the input shaft torsion bar by determining the torque vs. angle characteristics
- leakage
measurement of return flow at various hydrostatic pressure conditions, or as a function of the input shaft applied torque when the rack is locked
- return response (ability)
rack response to return to center position from an end position under different pressures
- pressure drop
measurement of the test fluid pressure at a predefined flow rate
- gear ratio
measurement of ratio of input shaft speed to rack speed for variable ratio transmission mechanisms
- poppet functionality
confirm the functionality of externally-actuated, pressure/flow modifying poppet check valves
- poppet adjustment
tuning of poppet valve response to desired parameters
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Electric power steering tests:
- module start-up sequence
precondition unit to break in all internal components
- calibration
position sensor calibration for end-stops and center position, torque sensor calibration for proper zero and sensitivity parameters
- functionality
confirm the proper functionality of position and torque sensors
- maximum torque
set output shaft load to the maximum value, and measure torque while the input shaft is rotated under constant acceleration
- back-driving torque
measure maximum input torque as the shaft is rotated though full stroke with no power to the unit
- steering limit protection
measure steering assist ratio vs. shaft angle when the input shaft is rotated from the center position under a fixed output shaft load
- PWM current draw
measure assist ratio, PWM current draw, and duty cycle under different fixed output shaft loads
- dead-band
measure assist ratio under various output shaft loads, when a precise input torque is applied
- directional change effort
measurement of input shaft torque when it is rotated from a clockwise to a counterclockwise direction under a fixed output shaft load
- steering bumpiness
measurement of input torque vs. time as the input shaft is rotated to a specific position under a fixed output shaft load
- self-return
rotate input shaft in both directions until the end-stops are reached, and measure time and torque to return to the center position
- power consumption test
measure voltage and current draw of the electric servo motor
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