In this paper, we describe design and development of a 3-axis proportional-integral-derivative (PID) controller for a holonomic precision inchworm robot. The mechanism has two Y-shaped electromagnets and six piezoelectric actuators (PAs) for obtaining 3-degrees-of-freedom (3DoF) motion on well-polished ferromagnetic surfaces. To measure its 3DoF position simultaneously, an integrated 3DoF inner position sensor composed of 4 linear encoders are developed. In experiments, we have checked that this arrangement of the encoders is valid for measuring the 3DoF motion under a condition without disturbance. To be robust against the disturbance, we also discuss requirement of an acceleration feedforward controller with 3 motion sensors to detect disturbance and slips of supporting electromagnet. This paper is first article which demonstrates simultaneous 3-axis PID control with nanometer-scale positioning resolution of miniature mobile robot driven by PAs. We also discuss about the future direction of the realization of compact, precise, fast, flexible, and energy-efficient mobile robotic factory.

In this paper, we describe a newly proposed design of an integrated three-degrees-of-freedom (3DoF) inner position sensor for an omnidirectional and holonomic inchworm mobile mechanism. The mechanism has two Y-shaped electromagnets and six piezoelectric actuators for obtaining 3DoF inchworm motion on well-polished ferromagnetic surfaces. We calculate conversion equations from four measured distances to X-, Y-, and θ-axis motion. We also explain how to make the input signals to realize the minimum time trajectory of free electromagnets with a newly proposed special kinematic model as an additional condition for energy-efficient control. Details of the design and performance are also described to realize flexible, compact, and high-accuracy positioning in precision engineering.

In this paper, we describe the design and development of the newly developed 3-DOF inchworm mechanism with 6 contact points on a surface to improve a positioning repeatability. The mechanism consists of a pair of Y-shaped electromagnets and six piezoelectric actuators and moves like an inchworm. We calculate a 3-DOF simple harmonic vibration model to get input signals in any 3-DOF motions. In several experiments, we confirm that the mechanism has better positioning repeatability than in previous mechanisms with 4 contact points, especially when the mechanism carries a payload. The design details and basic performance are described to contribute to flexible precise positioning technology.