The inchworm motor is a device using piezoelectricactuators to move a shaft with nanometer precision. The term is a trademark of the patent holder for this scheme, Exfo. Piezoelectricity is the ability of certain crystals to produce a voltage when subjected to mechanical stress. ... An actuator is the mechanism by which an agent acts upon an environment. ... A nanometre (American spelling: nanometer) is 1. ... A trademark (Commonwealth English: trade mark)[1] is a distinctive sign of some kind which is used by a business to identify itself and its products and services to consumers, and to set the business and its products or services apart from those of other businesses. ... A patent is a set of exclusive rights granted by a state to a person for a fixed period of time in exchange for the regulated, public disclosure of certain details of a device, method, process or substance (known as an invention) which is new, inventive and useful. ...
The inchworm motor uses three piezo-actuators connected together. The outer two actuators can independantly grip the shaft, the middle one is used to change the spacing between the end actuators. To move the shaft in a direction the first actuator grips the shaft, then the second actuator enlarges moving the first actuator and the shaft it is gripping away from the fixed location third actuator. When the middle actuator has reached its maximum increase the third actuator grips the shaft and the first actuator releases the shaft, the middle actuator returns to its normal size; the process can now be repeated. The process can also be reversed to move the shaft in the opposite direction.
If the expansion of the center actuator is precisely calibrated (and the two outer actuators do not slip) then the position of the shaft can be precisely controlled while having substantial travel distance.
External links
An explanation of the motor operation principle on Exfo's website
As an inchworm moves forward it has the opportunity to sense what is in front of it without having to commit to attaching to an inappropriate surface.
The strength of an inchworm's attachment to a surface li es in the way its foot pads grip the material it is attempting to move over.
In addition, the inchworm managed to maintain a firm grip on the surface at all times while the tracked vehicle displayed a tendency for the upper track to slip as the slope was increased.
Thus, it is desirable to reduce the failure mode of cracking and arcing due to tensile stressing of the materials, thereby increasing the reliability and life of the apparatus.
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