A spatial impedance controller for robotic manipulation

Mechanical impedance is the dynamic generalization of stiffness, and determines interactive behavior by definition. Although the argument for explicitly controlling impedance is strong, impedance control has had only a modest impact on robotic manipulator control practice. This is due in part to the fact that it is difficult to select suitable impedances given tasks. A spatial impedance controller is presented that simplifies impedance selection. Impedance is characterized using ¿spatially affine¿ families of compliance and damping, which are characterized by nonspatial and spatial parameters. Nonspatial parameters are selected independently of configuration of the object with which the robot must interact. Spatial parameters depend on object configurations, but transform in an intuitive, well-defined way. Control laws corresponding to these compliance and damping families are derived assuming a commonly used robot model. While the compliance control law was implemented in simulation and on a real robot, this paper emphasizes the underlying theor

Sliding mode control of spatial mechanical systems decoupling translation and rotation

This paper looks at the robust trajectory control of spatial mechanical systems using sliding mode techniques. Two distinctions of the proposed method from reported methods are: (1) The measure of attitudinal error used is intrinsically defined, Euclidean-geometric, and intuitive. From Euler's theorem it follows that given a desired and actual attitude of a rigid body there exists an axis and angle of rotation relating the two attitudes. This defines a relative rotation vector, which is used as an intrinsically defined, intuitive measure of error. Reported methods use algebraic differences of entities such as generalized coordinates representing attitude. While functionally correlated to attitudinal error, these measures are not intrinsically defined. (2) A novel, dynamically nonlinear sliding function is used that results in a simple control law. The parameters of this function are dynamically and geometrically intuitive. Simulation results are given for a spacecraft tracking a complex desired trajectory

CONFIGURATION ESTIMATION OF GOUGH-STEWART PLATFORMS USING EXTENDED KALMAN FILTERING

This paper develops extended Kalman filtering algorithms for a generic Gough-Stewart platform assuming realistically available sensors such as length sensors, rate gyroscopes, and accelerometers. The basic idea is to extend existing methods for satellite attitude estimation. The nondeterministic methods are meant to be a practical alternative to existing iterative, deterministic methods for real-time estimation of platform configuration.

Spatial Compliance Modeling Using a Quaternion-Based Potential Function Method

. This paper looks at the modeling of elastically coupled rigid bodies. The elastic deformation is assumed to be localized, which in particular is a valid assumption for exural joints. A generic, lumped paramter, Euclidean geometric, potential function based approach is presented using quaternion calculus. The potential functions are similar to functions presented in the spatial compliance control literature. Rigid body displacements are represented using a combination of Cartesian coordinates and quaternions. To demonstrate the utility of the proposed methods for computer analysis, a nontrivial example is considered. The system consists of two rigid bodies coupled by an asymmetric exure incorporating crossed leaf springs. While the compliant constitutive equations are well dened for arbitrary rigid body displacements, it is only claimed that the model is accurate for small displacements. Keywords: exible multibody dynamics, spatial compliance, exural joints, quaternions, spatial..