DSM has taken on many extreme environment actuator design challenges. Work has primarily been in piezo actuators but extends to some experimental techniques as well. Work has been in both the public and private sectors. DSM woulld like to use and develop its existing technology to design for more extreme environment challenges - Development@dynamic-structures.com
Examples of DSM's cryogenic research efforts.
Cryogenic Linear Valve Actuator
Challenge: Develop an actuator with up to 1.5 in of stroke, 0.5 in/s velocity, and capable of actuating up to 250 lb's of force. This actuator must be able to withstand temperatures down to 4 K (liquid helium). This actuator is intended to actuate a valve controlling cryogenic propellant fluid.
Solution: DSM developed and patented technology which integrates simple mechanical concepts that minimize cost and ensure reliability. This simplistic approach was also crucial in the actuator's operation at low temperatures. After validating the technology a family of actuators were created, each a different size, to fully characterize the technology.
Characterization of Piezoelectric Cryogenic Actuators
Challenge: Provide empirical data to characterize the reliability of piezoelectric stacks for use in cryogenic valve applications.
Solution: DSM documented the physical and electro-mechanical properties of several makes and models of piezoelectric stacks. Statistically relevant quantities of each make and model were endurance tested in cryogenic conditions to determine the cryogenic lifecycle characteristics of commercially available stacks. Mechanical shock and vibration lifecycle test were also undertaken. The resulting data provided our customer with the confidence they needed when selecting components for a critical life-supporting system for their aerospace application.
Cryogenic Rotary Piezo Motor
Challenge: Design a rotary motor mechanism that can operate between 25 K - 400 K. The motor should provide very low out-gassing and be capable of operating in a hard vacuum.
Solution: DSM was able to meet spec's required down to 80 K. A video is shown below which demonstrates the performance in liquid nitrogen (LN2)
Compact Piezo (PZT) Actuator for Cryogenic Isolation Valve
Challenge: Design and build a valve that our customer could use to control a thermodynamic vent system
Solution: Using patented Flexframe Piezo ActuatorTM technology, DSM designed a built a system that allowed for proportional modulation of flow in a smooth voltage controlled manner. The actuator was constructed from Invar 36 in order to minimize temperature sensitivity. Flexframe technology eliminates the need for bearings, bushings or lubrication which eliminates the possibility of binding as a result of thermal contraction/expansion mismatches. The final actuator design measured approximately 56 x 19.5 x 15mm (2.2 x 0.77 x 0.59 in), weighed less than 75 grams and produced more than 300 microns of displacement. In order to provide our customers with proven solution, DSM performed endurance and reliability testing at cryogenic temperatures to validate the performance of the final design.
High Force, Cryogenic Linear Actuation
Challenge: Researchers at NASA asked DSM to design and build a high force piezoelectric motor for macro positioning in extreme environments.
Solution: Using patented technology, DSM developed the I-90 step-and-repeat motor. Measuring just 63 mm x 57 mm x 18mm (2.5in x 2.3in x 0.7in), this compact motor is capable of generating an output force of 90N (20.2lb) with a total stroke of 25mm (0.98in) and speeds of up to 30mm/sec.
High Temperature Operation
Nonmagnetic, Vacuum Rated Piezo Actuator
Challenge: Provide a high stroke, high resolution, non-magnetic actuator capable of operating at high temperature and vacuum conditions. Actuator will control the thrust vectoring of a space ion engine.
Solution: As part of a program funded by the European Space Agency, piezoelectric actuators made by DSM were integrated into a T5 gridded ion engine. The actuators were used to “steer” the engine by moving the screen grid relative to the accelerating grid. It was necessary to design a non-magnetic actuator that could operate successfully at high temperature and vacuum condition. Trials up to 250 ºC were successfully performed, without adverse effect despite many thermal cycles. The system operated properly for two weeks of continuous testing during engine trials. DSM was able to collect valuable data concerning the behavior of ceramic piezoelectric material at high temperatures.
Vacuum Rated 3-Axis Linear Piezo Positioning
Challenge: Provide a 3 axis positioning system that can be used in a vacuum environment.
Solution: When one of DSM's customers required a custom three-axis positioning system, DSM leveraged the flexure-based design of its flextensional piezo actuators to create independent X, Y, and Z stages. The resulting X and Y stages each provide 200 microns of travel, and the Z axis has a stroke of 500 microns. The original stage assembly was designed for vacuum compatibility and was provided with benchtop models of DSM's VF linear piezo amplifier. The basic design of the stage system is scalable to smaller/larger displacement capabilities. As a follow-on deliverable to the original, open-loop XYZ system above, DSM's customer requested closed-loop capability for the X and Y axes. DSM incorporated capacitive probes and used SA-100 linear servo amplifiers to provide stand-alone servo control. A 24-bit analog input accepts the position target signal, and digital I/O provides flags for "in-range" and data acquisition triggers.
Vacuum 3-Axis Rotary Kinematic Mount
Challenge: Deliver a 3-axis optical mount for use under vacuum.
Solution: DSM used its experience in flexure mechanisms to design a backlash- and stiction-free 3-axis rotary mount capable of supporting a 4kg payload. The design requirements included +/- 2 mm of linear travel adjustment in one axis and +/-2° of rotational adjustment in two additional axes. DSM designed the flexure mount using a titanium and aluminum construction. Fine thread screw adjusters provide manual adjustment capability. Pre-load springs and flexure pivots provide return force. Special attention was paid to ensure the assembly's design minimizes undesirable motion during temperature transients and shock loading.