SOLID Learning Robot – Solid State Actuators

“ANALYSIS: Solid State Actuators provide the most exotic but costly type of actuator, best suited to very small deflections and operations in hostile environments such as vacuum.

The most innovative actuator option for our SOLID Learning robots is the Solid State Actuator, which can be found in some camera image-stabilization systems and are available through specialty and online electronics suppliers.

Nitinol Shape Memory Alloy (SMA) wire - called "Muscle Wire"

The small bundle of wires represents the movement articulation mechanism for a lightweight robotic hand, provided for my STEMulate Learning workshops by its manufacturer, Dynalloy. This is a form of Nitinol Shape Memory Alloy (SMA) called Muscle Wire, which physically shrinks in length when an electric field is applied.

Shape Memory Alloy (SMA) Linear Actuator

By connecting several pieces of SMA material, it is possible to create solid state linear actuators capable of great strength in very small packages because there are no complex assemblies of moving parts, gears and motor rotors.

Shape Memory Alloy (SMA) Rotary Actuator by MigaSMA wire wrapped around a rotary cam allows the creation of a very small solid state rotary actuator capable of movement within a 120 degree arc (a third of a circle, +/- 60 degrees rotation from center). This is less than the 180 degree arc provided by standard mode Servos, but requires no other mechanical components and has a high output power to weight ratio.

Amplified Piezoelectric Linear ActuatorIn addition to Shape Memory Allow (SMA) materials, other solid state actuators are formed using electrostrictive or piezoelectric materials. Augmented piezoelectric linear actuators are used in precision medical and industrial equipment, but are only able to move a few millimeters across a full stroke cycle.

Rotary Piezoelectric Actuator for Space Robotics

Piezoelectric rotary actuators are used almost exclusively in applications meant for operation in vacuum and microgravity, operating without need for volatile lubricants or complex moving parts that may be influenced by the environmental conditions of space.

Piezoelectric MotorEven full-rotation piezoelectric motors are available, operating through a sequential micro-contracting of piezoelectric components to create individual steps forward or backwards in much the same manner as stepper motors. These options, like all solid state actuators, are specialty items carrying a very high cost and available in a limited number of configurations. Most solid state actuators are controlled by simple variation in electrical current, but only operate across a small range of deflection.

Summary for Solid State Actuators:

  • Price: Extremely High (thousands of dollars and up) with additional components required
  • Availability: Sourced from some cameras and some electronic component suppliers
  • Control: Requires additional components for control
  • Operation: Very accurate positioning within operative arc, movement stroke or in continuous rotation based on implementation
  • Outputs: As per the configuration and type of solid state material employed
  • Caveats: Not commonly available, often very expensive, some options designed for operation in hostile environments such as space

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