Performance of a servomechanism that provides accurate, continuous control of mechanical power is fundamentally governed by the actuator used to meter power to the load. These actuators, when used in exacting control applications, tend to be complex, expensive, and critical. This paper describes a mechanical servoactuator concept based on the toric-transmission principle that has the potential of providing precise power control in a relatively simple and rugged package. Actuator kinematic principles are explained and equations that describe these relationships are presented to illustrate both steady-state and dynamic performance characteristics. Closed-loop control techniques are discussed with specific emphasis on the load-acceleration control feature inherent with this actuator concept. Experimental performance data obtained from testing a 1-hp prototype model operated as a velocity servo are presented. Static velocity control accuracy of ±0.1 percent is readily obtained; transient-response times vary from 20 to 40 milliseconds depending on signal amplitude and load conditions.

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