Control system for hydrostatic transmission

A control system for controlling a hydrostatic transmission having an engine driven variable displacement pump coupled to a fixed displacement motor, the pump having a swashplate which is controlled by a control signal generated by the control system, the control system comprising:

• a speed command signal generator;
• a motor speed sensor for generating a sensed motor speed signal:
• an engine speed sensor for generating an engine speed signal;
• and
• a control unit which generates the control signal as a function of the speed command signal, the sensed motor speed signal and the engine speed signal, the control unit generating a desired motor speed signal as a function of the speed command signal and the engine speed signal, generating a desired swashplate angle signal as a function of the desired motor speed signal, generating a difference signal as a difference between the desired motor speed signal and the sensed motor speed signal, generating a proportional signal by applying a proportional function to the difference signal, generating an integral signal by applying an integral function to the difference signal, generating a derivative signal by applying a derivative function to the difference signal, generating a sum signal as a summation of the desired swashplate angle signal, the proportional signal, the integral signal and the derivative signal, and generating the control signal as a function of the sum signal.

A control system for controlling a hydrostatic transmission having an engine driven variable displacement pump coupled to a fixed displacement motor, the pump having a swashplate which is controlled by a control signal generated by the control system, the control system comprising:

• a speed command signal generator;
• a motor speed sensor for generating a sensed motor speed signal;
• an engine speed sensor for generating an engine speed signal;
• and
• a control unit which generates the control signal as a function of the speed command signal, the sensed motor speed signal and the engine speed signal, the control unit generating a desired motor speed signal as a function of the speed command signal and the engine speed signal, generating a desired swashplate angle signal as a function of the desired motor speed signal, generating a difference signal as a difference between the desired motor speed signal and the sensed motor speed signal, generating an integral signal by applying an integral function to the difference signal, generating a sum signal as a summation of the desired swashplate angle signal and the integral signal, and generating the control signal by applying a lead-lag function to the sum signal.