A single small actuation system that provides high resolution [step size] of 2 nanometers (nm) over an extended range of 20 mm with consistent forces of 100 Newtons [peak values exceed 180 N] and integral power-off hold is described. Speeds of 60 mm/second can be shown but electronic efficiencies are much higher at 1 to 10 mm/s. Open- and closed-loop control is described. Progress on potential applications in adaptive optics, large optical beam control, and photonic and semiconductor test and measurement are noted. New data is presented showing ± 5-nm control of 100 Newton loads. Heat generation is estimated to be very small [110 mJ/hr] while actively holding position. Comparison of encoder and capacitance gage stability over time and temperature is discussed because it affects control in the 5-nm regime. This response can be contrasted with previous 2 kHz over 30-micrometer response for vibration or adaptive optics control. Performance of a new Class D switching amplifier that offers higher efficiencies at peak demands is described. The actuator design uses a set of three piezoelectric elements. These constitute 1100 nF of load. High speeds in the 20 to 60 mm/s range [up to 2500 Hz clamp change cycles] significantly affect power needed and design efficiencies. Alternative design options are presented with rationale for present design choices and resultant performance. The basic design allows for choices based on performance needed.
Systems that require multiple actuators for range and precision, such as adaptive optics, large optical beam control, photonics metrology, and semiconductor test-measurement, are candidates for this evolving actuator system. Designers can now consider one system to provide over 100 N force in nanometer steps at up to 50 mm/s with features such as, greater than 20 millimeter travel, power-off hold, high acceleration, and high stiffness. High mechanical power density is beneficial whether fitting an actuator into limited real estate or minimizing total mass for launch or inertia considerations. Smaller mechanical systems benefit from higher stiffness and are less susceptible to environmental transients. The actuator design uses sets of three piezoelectric elements. These constitute 1100 nF of load driven at up to 2500 Hz. In addition to the mechanical actuator, a new high efficiency amplifier and controller are being developed. Total system power density benefits will be noted and clamp design detail is presented.
Photonic assembly packaging, adaptive optics, large optical beam control, and semiconductor test and measurement are application areas that have needs for nanometer-level precision. Utility is increased with features such as greater than 10-millimeter travel, power-off hold, high acceleration and high stiffness. Alignment applications can benefit from a high mechanical power density. This translates into smaller package size for required force, speed, travel and resolution performance. In manufacturing of photonic packages, the space around the work piece often is limited and ergonomic design considerations for workspace are helped with a small profile. Smaller system size implies less total mass and power required for a given performance level, which is highly desirable for airborne or space applications. Smaller mechanical systems benefit from higher stiffness, lower Abbe error, and are less susceptible to environmental transients. A second-generation actuator system that provides about one nanometer open loop step size with 25 millimeters of travel will be characterized. The first-generation model provided more than 100 N force at 25 mm/s speed. The device is compatible to using proprietary thin film and MEMS technology for a high-friction clamping design that simulates an “infinite gear”.
Alignment stability, maintaining a minimum loss state in optical power during product fabrication, is one factor in evaluating processes and equipment for assembly and testing of fiber-optic/optical components. Cost reduction through yield improvement will require some level of alignment automation. To illustrate the changes in optical power over time and dimensional change, a 6-axis commercially available alignment robot has been characterized by aligning a single mode fiber to a single mode fiber and to a planar lightguide circuit. Optical and mechanical performance (resolution, repeatability, and stability) is presented and correlated. External factors affecting the automation system's optical performance are discussed.
Assembly and measurement of photonic subsystems or integrated optical components is transitioning from manual to semi-automated and fully automated configurations. Controlled motion, which allows movement in the 10-millimeter range with resolution of nanometers, is a critical requirement for successful assembly or functional verification of an assembly. Application specific requirements may include holding position at sub-micrometer levels for hours, repeatability of 0.1 percent over 100 micrometers to 0.005 percent over 10 millimeters, and simple controls for systems as basic as 2 degrees of freedom to multiple robots with 6 degrees of freedom each. New clamping technology, in an INCHWORM(brand motor, utilizes a combination of MEMS fabricated features and proprietary clamp interface materials to increase the clamp friction. This allows much higher push forces to be generated or the design freedom to trade force for size. Power versus Force curves are presented. Resolution, velocity, stiffness, and simple control are maintained in a much smaller package. Single mode fiber optic devices have active areas in the 5-10 micrometer range. Assembly needs are going smaller. A relatively powerful motor with dimensional resolution and time stability that can be incorporated into ever smaller robots will be needed to meet future photonic automation requirements.