Piezoelectric stacks are the core components of DSM’s SRM actuators. Since the single move  displacement of piezoelectric ceramic stacks is very  small, SRMs consist of a mechanism to convert  many small steps into a single continuous move equaling the sum of the small steps. Generally, controlled  intermittent friction is used as the means of transferring the displacement of the piezoelectric ceramic stack to the output shaft or slider’s continuous motion. Spanner (2006) classifies piezoelectric motors into  two classifications: quasistatic, and ultrasonic motors. Quasistatic motors are further characterized by  those that operate on a clamping principle or inertial principle. DSM’s SRM actuators are quasistatic clamping motors. A typical clamping motor operation is described in Figure 2, which follows from the  Inchworm /g147 Motor patented by Burleigh Instruments, Inc. in 1975 (May, 1975). The motor has two sets of  piezoelectrically actuated mechanical clampers that alternatively grip (by applied friction) either end of the  output shaft. The extender moves the clamps relative to each other and the external frame to advance the shaft either to the right or left as the sequence dictates. Through the process of clamping and unclamping  the clamp elements and stepping the extender, the shaft advances.  Operating sequence 1) actuate clamp 1 2) release clamp 2 3) extend shaft 4) actuate clamp 2 5) release clamp 1 6) contract mid section 7) repeat Velocity control step size - voltage# of steps - frequencyShaftFriction MaterialClamp 1 Clamp 2Extender Shaft output motion Figure 2 – Operating Steps Of A Step And Repeat Motor After The Patent By May (1975)  Numerous piezoelectric motors have been developed in the last 6 years through a DARPA initiative called  the Compact Hybrid Actuator Program or CHAP. Three motors demonstrated reasonably high levels of  mechanical output power when compared to previous generations. Of the three motor actuators, the  Kinetic Ceramic (2004) unit is the most powerful - achieving up to 40Watts of mechanical power. An  advanced Burleigh unit (Burleigh, 2005) has approximately 600 times more power than the current  Inchworm /g147 motor but it produces only 2.5 Watts of mechan ical power. In the UCLA MADD device  (Carman et al, 2001), silicon microteeth are used but are limited in strength resulting in a 1.1-Watt  maximum output. The Kinetic Ceramic motor delivers ap proximately 40 Watts of mechanical power  through a hydraulic interface that requires hydraulic tubing and valving to deliver motion to the load.  Description of DSM’s High-Force SRM Mechanism  DSM’s SRM design uses a spring-biased clamper plate mechanism and other proprietary innovations  within the motor to significantly improve drive force relative to current commercial SRMs. Shown in Figure  3 are the components of DSM’s motor architecture. The minimal components include an extender  element, a single active clamp, a static clamp, friction interface components, and the novel clamper plate.  While DSM’s current designs can all be operated with only one active clamp, most use two active clamps  to increase the motor drive force. The extender resides directly in the moving shaft and advances the clamp element relative to the non-moving frame. In this configuration, DSM’s design is an inversion of the  traditional step and repeat motor with the clamper elements moving with the shaft while the location of the  clamper plate remains stationary. DSM has also created a motor configuration with fixed clampers that uses the novel clamper plate and has an extender with a friction interface at each end. Either  configuration with the novel clamper plate design offers higher drive forces than traditional SRM  mechanisms and a means for self-compensating for temperature change and clamping surface wear.   2