A multi‐purpose dynamic and tactile sensor for robot manipulators

Abstract

In this article, a multi-purpose tactile/acceleration sensor system made of newly developed thick polymeric piezoelectric material and capable of sensing acceleration, contact force and pressure is developed and evaluated using analytical and experimental techniques. The sensor system is discretized and modeled by a single degree of freedom second order system from which equations of electromechanical dynamics are formulated to evaluate its performance. Analytical solutions are compared favorably with experimental results. INTRODUCTIONAccurate acceleration, force, and pressure measurements provide information to robotic system for high precision manipulation and control in performing various tasks. In various sensor designs for dynamic measurements and control, piezoelectricity is probably the most widely used electromechanical characteristics. In general, piezoelectric material responds to mechanical forces and/or pressures and generates an electric charge which is referred to as the direct piezoelectric effect. Conversely, application of electric field to the material can produce mechanical stress or strain which is named as the reciprocal, or converse piezoelectric effect. Temperature change also affects electric polarization on some 720 Journal of Robotic Systems-7987piezoelectrics, which is referred to as the pyroelectric effect.' The Curie brothers, Pierre and Jacques, first observed piezoelectricity in natural crystals in 1880.2 Brain investigated piezoelectric polymers in 1924.3 Kawai discovered piezoelectric polymeric polyvinylidene-fluoride (PVDF) in 1969.4 Bergman' and McFee6 also found pyroelectric properties in PVDF polymer PVDF is pliant, tough, lightweight, and flexible and can be made in large flat sheet. On the contrary, piezoelectric ceramics and natural crystals are usually dense, brittle, stiff, and difficult to produce large size and impractical to fabricate into complex shapes. In applications of the synthetic piezoelectric materials to dynamic measurements and control, the flexibility, continuous surface area, dimensional stability, arbitrary geometric configurations, and low production cost of the PVDF polymer do provide great advantages over other crystalline materials, which directly result in increasing its popularity since the mid-1970'~.'.~ Thin Tzou and Pandita: Multi-Purpose Dynamic and Tactile Sensors 72 1 FORMULATION Piezoelectricity in Thlck Polymeric PVDF Fiat piezoelectric material can be generally expressed in a complex matrix form:The relationship between electric polarization and mechanical strain/stress in

2D semi-analytical solutions for single layer piezoelectric laminate subjected to electro-mechanical loading

“…For a commonly used piezoelectric material like PVDF, which falls in the crystal group Rhombic and Class 7, the piezoelectric constant matrix due to Cady [26] and dielectric constant matrix due to Tzau and Pandita [27] are given by; …”

Cylindrical bending of piezoelectric laminates with a higher order shear and normal deformation theory

“…The piezoelectric constant matrix [e] and the dielectric matrix [g] for polyvinyledene fluoride (PVDF) commonly known as PVDF polymer are given in [31,32] and the Maxwell's charge equilibrium equation [33] can be written as…”

Effect of Crystal Orientation on Piezoelectric Response of Single-Crystal Piezoelectric Layers

“…Piezoelectric materials have been widely used as sensors 1 and actuators 2 in a variety of applications, such as microcantilever sensors for the detection of proteins and cells in biological fluids and actuators for portable peristaltic micropumps. The electromechanical coupling in piezoelectric materials provides a unique method to control structural response by electric loading and to sense structural deformation from the change in electric field.…”