Multi-axis motion generator utilizing feedforward control

Abstract

Apparatus for generating synchronized multi-axis intermittent motion utilizing electronic encoding, memory and a position control system having feed-forward control. A plurality of slave shafts are rapidly and accurately positioned in response to the positioning of a rotatable master shaft, without mechanical interconnections therebetween. An analog transducer is attached to the master shaft providing an analog position output which is fed to a master encoder which feeds a digital output to a plurality of independent digital memory devices. Each digital memory device provides, in response, an output digital signal indicative of the desired position of an associated slave shaft. The output of each memory device, through an appropriate digital-to-analog converter, is fed to a position controller which positions the associated slave shaft as desired. The servo controller includes a feedforward input to speed positioning and reduce system lag. The feedforward velocity signal is obtained by calculating the difference between the present position of the associated slave shaft and the desired future position of the slave shaft to obtain the desired change in the slave shaft position. This difference is multiplied by the absolute value of the master axis velocity to obtain the necessary velocity feedforward signal. The velocity feedforward signal, which is a function of the change in slave shaft position and the velocity of the master shaft represents the velocity at which the slave shaft must be rotated to achieve the desired position while the master shaft moves through one digital increment.