| Abstract |
Linear motion is interesting in various applications fields such as automotive, medical or
heating/ventilation/air conditioning. Linear actuators are used for flow rate regulation purposes.
Knowing their characteristics and analysing their behaviour are important to improve the
performances. An original DSP controlled automatic test bench has been designed and developed to
characterise linear actuators, with low manual handling and enhanced measurement accuracy.
The mechanical elements of the test bench consist in a load part and a test part coupled through a
spring. A force sensor is placed between the load part and the spring. A linear optical encoder, fixed
on the test part, directly measures the position of the test part. The measurement process takes place in
two phases: first, the stress is applied on the actuator using the feed-back loop (DSP 1 in "force
regulation" mode). Secondly, the actuator is started through the "DSP 2 frequency generator". The
load part position is controlled according to the actuator position (DSP 1 in "position follower" mode).
The absolute position and the force signals are acquired during displacement cycle.
The 2 main measurement processes are based on a dichotomous method. To reach the maximal force
of the actuator, the load is increased or decreased depending on the result of the previous
measurement.
The test bench is able to draw the following characteristic curves: force vs. current, force vs. speed,
backlash/precision/stiffness/hysteresis vs. position and reverse force. |
