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The future of clutch technology

The hydraulic clutch actuator

Background

This project is a collaboration between Linköping university and Scania CV AB in which eight students are going to evaluate a concept in an existing fully hydraulic rig used to actuate a clutch. Today the clutch is actuated using a pneumatically assisted eletro-hydraulic system. A fully hydraulic system will produce less strain on the battery, but the system still has to meet the performance requirements of todays system. The task is to evaluate the control performance of the hydraulic system in simulation environment and later implement the chosen control strategy on the rig. The challenge was to achieve the same behavior on the rig as in the simulation environment because of the appearing non-linear phenomenon in the real system. The requirements that had to be met were as follows:

  • Reach 90 % of the final value in 180 ms
  • Maximum overshoot should not be greater than 0.2 mm
  • 100 ms after reaching 0.5 mm from the final value, the maximum position error should not be greater than 0.1 mm
  • The test rig

    The rig was equipped with a real sized clutch, a pump, two pressure relive valves, one control valve, one cylinder and three sensors. The couple and decouple was done by pushing the cylinder onto a diaphragm spring with a force up to 6250 N. The control valve was controled with an Arduino Uno, which also measured the signals from the sensors.

    An image of the test rig
    This is the test rig used in the project.

    Control System

    The control system is based on a cascade control method. This method utilizes several measurement signals in order to calculate the control signal. The feedback signal in the inner loop are current to the valve, in the outer loop the feedback is cylinder position. Disturbances in the inner loop will be dealt with and their contribution on the regulated cylinder position will be cancelled.

    An image of the controlsystem
    This is the control loop used for the system.