A novel linear piezoelectric inchworm actuator based on a ratchet mechanism

A new working principle of inchworm actuator, which converts vibrations of a single piezo actuator into unidirectional step movement of a mover via a ratchet mechanism, was proposed. The proposed working principle has the following priorities: (1) it requires only one piezoelectric actuator which greatly simplifies its driving signals and driving circuits; (2) it can achieve a large driving speed with little compromise of a large force output while maintaining a high positioning precision of piezoelectric actuator and a theoretically unlimited motion range, although it can only achieve unidirectional movement with unidirectional self-locking capability; (3) it could be open-loop controlled with no accumulated step errors. The proposed actuator was designed with compliant mechanism and an analytical model of the design was developed, validated by finite element simulations carried out in Commercial Software ANSYS and used to guide the selection of design parameters. A prototype was fabricated and tested. Experiments show that the proposed actuator achieved a speed larger than 12 mm s⁻¹, a driving load larger than 60 N in the moving direction, a reliable open-loop controllability with no step accumulated errors even under driving load variations of 60 N, and a working range larger than 1 mm with a high positioning precision around 320 nm under closed-loop control, which validated the superiorities of the proposed actuator.