The controlled retardation of Ward Leonard drives

The behaviour of minimum-time-response second-order control system is widely known, and in the paper the philosophy of this type of response is extended to the problem of the control of a third-order drive responding to a step in output displacement. The minimum time response of a system is related to physical limitations of the system in respect of speed, torque (i.e. acceleration), and rate of change of torque. These limitations define the characteristics of the optimum traverse cycles, and relationships are derived that may be used to design a controller for operating a drive in accordance with these cycles. These principles have been used to construct a model incorporating a 3 kW Ward Leonard drive. Satisfactory performance is demonstrated with positive and negative load torques and with a substantial change in load inertia.