Investigation of a cable-driven parallel mechanism for interaction with a variety of surface, applied to the cleaning of free-form buildings

In this paper, the capability of a specific cable-driven parallel mechanism to interact with a variety of surfaces is investigated. This capability could be of use in for example the cleaning of large building surfaces. A method is presented to investigate the workspace for which the cables do not interfere and a surface interaction force can be generated. This method takes into account the influence of cable mass. As an example, this method is used for the design of a mechanism with a workspace conform to the dimensions of a typical building facade. The mechanism is concluded to be feasible as long as there is room to locate the pulleys at an adequate distance from the surfac

A cable-driven parallel mechanism for the interaction with hemispherical surfaces

In this paper, a device based upon a specific cable-driven parallel mechanism to interact with hemispherical surfaces is proposed and investigated. This device could be of use in, for example, the automated cleaning of glass domes. Because the cables move on the hemispherical surface, they are curved. A method is developed to calculate the inverse kinematics and the workspace of this mechanism. This method and device are applied to and evaluated for an example of a large glass dome, showing its potential for this purpose

Kinematic Calibration of a Six DOF Flexure-based Parallel Manipulator

The absence of friction, hysteresis and backlash makes flexure-based mechanisms well-suited for high precision manipulators. However, the (inverse) kinematic relation between actuators and end-effector is far from trivial due to the non-linear behaviour of the deforming compliant joints. In this paper we consider the kinematic modelling and calibration of a flexure-based parallel manipulator for a six degrees of freedom (DOF) mirror mount. The mount is positioned by six arms, each of which has five joints and is driven by a linear actuator. Three kinematic models are compared. A simple and computationally fast model that ignores pivot shift is too inaccurate. A flexible multibody model can account for the non-linear deformations of the joints, but is too computationally expensive for real-time applications. Finally, a kinematic model is derived using the Denavit–Hartenberg notation where the pivot shift is described with a polynomial approximation. This model offers nm accuracy with a small number of terms from a Taylor series and can be evaluated sufficiently fast. In this way a nominal kinematic model can be derived using the (kinematic) parameters from CAD data. However, the achievable accuracy in an experimental set-up remains inadequate. Hence a geometric calibration procedure has been developed for the four most critical translations and rotations of the end-effector. The measurement set-up contains two position-sensing detectors to measure these motions. The model is linearized for small errors in the parameters to enable the use of linear regression techniques. With a least squares estimate the errors in the parameters are estimated. The quality of the estimation is checked by combining the singular value decomposition of the (linearised) regression matrix with cross-validation. It was found that the kinematic calibration clearly improves the accuracy of the (inverse) kinematic model