B-6 Control System MN1902B.2 Control system operationThe following sections describe the operation of the position, speed and torque controllers.B.2.1 Position controllerThe position controller, shown below, is a typical proportional + integral + derivative (PID)controller, with gains set by the Mint keywords KPROP, KINT and KDERIV. The positiondemand from the profiler is compared with the measured position and the error is fed into thePID control calculation. The resulting value forms the basic speed or torque demand,depending on the CONFIG setting. The effect of the integral term can be changed using theKINTLIMIT and KINTMODE keywords. KINTLIMIT sets the maximum value of the effect ofintegral action, as a percentage of the full scale demand. KINTMODE can be used to specifythe circumstances under which the integral term is applied.As an alternative to the derivative term, a velocity feedback term is available by settingkeyword KVEL.To improve the tracking performance of the position controller, the profiler speed is fed forward,by gain KVELFF, to give a contribution to the final speed or torque demand. The profileracceleration is fed forward by gain KACCEL to give a contribution to the final speed demand.The position control calculation is performed every 500μs.The gain values KPROP, KINT, KDERIV, KVEL, KVELFF and KACCEL must be tuned for eachapplication. This can either be performed automatically within the Commissioning Wizard, ormanually using the Fine-tuning tool in WorkBench v5.KVELFFKPROPKINTKDERIV KVELdtddtFollowingerror(FOLERROR)Proportional gain termIntegral gain termDerivative gain term Velocity feedbackterm Measured speed(VEL)Speed demandMeasured position(POS)Velocity feedforward termProfiler speed(VELDEMAND)Profiler position(POSDEMAND) ++++ ++--Figure 47 - Position control system
