High-output paraffin linear motors: utilization in adaptive systems

摘要

Abstract: High output paraffin (HOP) thermal actuators are used as linear motors in spacecraft mechanical systems. Heat energy to drive the devices is provided by either environmental temperature changes or electrically powered resistance heaters. Mechanical work is obtained from the 15% expansion of paraffin that occurs during the solid-to-liquid phase change. This paper describes the design and characterization of an HOP positioning actuator prototype (HPAP); an HOP actuator configured to provide accurate, high force positioning for adaptive systems such as space structures and optics. The HPAP provides a maximum 150 lbf over a displacement of 0.1 in. when powered with 20 W at 28 V ac or dc. Parameters critical to use in adaptive systems are characterized including dynamic response vs. load and power input, set-point accuracy, and accuracy vs. actuator velocity. With 10 watts of cooling available through conduction, calculated HPAP response time against a 100 lbf load is 7.9, 21, and 150 seconds for step changes of 10, 100, and 1000 $mu@m respectively. Measurement of the set- point accuracy was limited by the accuracy of the position measuring equipment ($POM .03 $mu@m). Test results indicate that HOP thermal actuators are appropriate for utilization in adaptive systems requiring high displacement, accurate positioning within a control bandwidth of 0.5 Hz or less. !3