Dynamic Inclination Measurement for Five Degrees-of-Freedom Robots

Vishesh Vikas and Carl D. Crane III

Keywords

Inclination measurement, Inertial measurement, Vestibular Dynamic Inclinometer, Dynamic Equilibrium Axis, five degreesoffreedom robot

Abstract

Inclination measurement for purpose of balancing of robots has traditionally been accomplished using Inertial Measurement Units (IMUs) which use linear acceleration measurement and gyroscope data. This provides inclination measurement relative to an absolute axis (or coordinate system) and is subject to drift. The Vestibular Dynamic Inclinometer (VDI), motivated by the human vestibular system in the human ear, has been introduced for inclination measurement in case of one-dimensional motion (rotation) of robots. This paper extends the Vestibular Dynamic Inclinometer (VDI) to inclination measurement for five degrees-of-freedom of robots (planar motion of the base and two degrees-of-freedom serial chain), thus, proposing the planar Vestibular Dynamic Inclinometer (pVDI). The proposed design of the pVDI sensor comprises of one triaxial gyroscope and strategically placed four dual-axis linear accelerometers. The concept of Dynamic Equilibrium Axis (DEA), the axis along which the robot/body is at equilibrium is also discussed. The inclination angle obtained from the pVDI is relative to the DEA. A closed form solution to calculate the inclination from the DEA, other inclination parameters and the magnitude of acceleration of the platform/surface of contact is discussed. The planar Vestibular Dynamic Inclinometer (pVDI) yields in the general case, irrespective of acceleration of the platform/surface of contact or sensor array location, a fully effective dynamic inclinometer, which continually senses the inclination from the axis of stability (DEA), and is not subject to drift or integration errors. As the purpose of robot balancing is to bring into alignment the robot and the axis of equilibrium, the inclination measurements obtained from the pVDI are ideal candidates for control input.

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