Hydraulic Servo Systems

Hydraulic servo system design is different in that there is generally not an independent control loop going on in front of the robot controls. The controller commands the servo valve for a flow and monitors the position directly. Force, inertia and changes in geometry all need to be considered in obtaining good response and path accuracy. What needs to be considered carefully is selection of the servo valve size. If a servo valve doesn't have the flow requirements necessary, it will under-perform and not follow the path very well. If it is oversized, it will overreact and not be stable until gains are reduced to compensate. When running with an oversized valve that normally has a range of +/- 10 volts to achieve maximum flow and maximum flow is never required, or desired, you end up working with far less resolution with the command voltage - maybe +/- 2 volts. It is ideal to size the system to utilize 80 to 90% of the servo valve's capacity for a good mechanical system.

Comments are welcome!

Some examples later. (Still under construction)


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