The clamper plate provides a constant clamping force to the motor actuator enabling zero power hold.  The clamping plate is on a pivot and it therefore transfers the clamping force from the active clamp to the  static clamp – leading to an operating condition where the clamping force is always present. DSM’s architecture also provides a much more consistent and significantly higher clamping magnitude than in  the traditional step and repeat motor. For exampl e, DSM recently developed a high-force IMPULSE  PiezoMotor™ with approximately 2000 N peak force (called IMPULSE 2000 for short) and 20 mm/s peak unloaded speed. Compare this to a COTS piezomotor linear actuator from EXFO (2007) with 9.8 N peak  force and 1.5 mm/s peak speed. For low-force applications and a small package, DSM is developing an  IMPULSE 30 (30 N of force) with 32 mm/s drive speed.   IMPULSE PiezoMotor™  mechanism details and factors that affect the force and step size are presented  relative to the components shown in Figure 3. Experi mental testing results are also discussed.  Sideplates  (dashed) provide rigid support of each end of shaft Extender drives active clamp back andforth relative to static clamp Active clamp clamps while lifting clamper plateStatic ClampClamper Plate transfers clamp action back and forth with each step Friction Interfaces  produces force  between clamps and clamper plate frame  Figure 3 – Operational Components And Mechanisms In DSM’s Step And Repeat Motor   Motor Drive Force  The first factor in determining motor drive force is the force capacity of the piezoelectric stack in the  extender element. DSM uses two common piezoelectric stack cross-sections of 3.5 x 3.5 mm2 and 10 x  10 mm2. The extension force capacity of these stacks is approximately 650 and 5000 N respectively at 50  MPa of drive pressure. DSM has designed the motor’s peak drive force to coincide with approximately  20% of the extender stack capacity. Therefore a design maximum for DSM’s IMPULSE PiezoMotor™ with  a single 3.5 x 3.5 mm2 piezoelectric extender stack would be 130 N of drive force. To obtain up to 2000 N  of drive force, DSM’s IMPULSE PiezoMotor™ uses two side-by-side 10 x 10 mm2 stacks. Figure 4 is a  picture of an IMPULSE 2000 prototype motor that was delivered to a NASA valve contractor for testing  with a propellant isolation valve and the IMPULSE 30 prototype.   The second factor in motor drive force is the clamping force applied by the clamper plate to the active and  static clamp components. The clamping force is applied via a spring that biases the clamped plate down onto the active and static clamps. The resulting clamping force is proportional to the spring force. The  product of the clamping force magnitude and coefficient of friction of interacting components dictates the  driving force for the motor. The size of the spring force that can be applied to the clamper plate is dictated  by the size of the piezoelectric stack used in the active clamp. A key aspect of motor design is balancing  the amount of spring force with the size of the active clamp piezoelectric stack. Through careful experimentation and analysis, DSM has derived a proprietary process for sizing the spring force and  piezoelectric stack for maximum driving force.   3