Solutions are developed for the effective implementation of parallel manipulators. A class of three-branch parallel manipulators, with three main-arm joints on a branch and a passive spherical branch end joint, is considered. All feasible combinations of revolute and prismatic joints and all feasible combinations of sensing/actuating of the main-arm joints are investigated.

Solutions for the forward displacement problem of the class of three-branch parallel manipulators are introduced. The effect of including redundancy in the main-arm joint displacement sensing on providing closed-form forward displacement solutions and on the reduction of the number of potential assembly modes for the manipulators is investigated. Intersection of loci defining the feasible locations of the branch ends considering individual branches and branch combinations is utilized for the solutions. It is found that closed-form solution exist for all cases of redundant sensing and for asymmetric non-redundant sensing.

The special configurations of parallel manipulators are considered. The investigation is based on examining potential degeneracies of the screw systems formed by actuated-joint associated wrenches, identifying all potential uncertainties for the considered class of manipulators. The characteristics of the unconstrained instantaneous degrees of freedom corresponding to each uncertainty configuration are discussed. Joint actuation layouts that eliminate the uncertainty configurations are determined through the consideration of all feasible cases of main-arm joint actuation.

The effect of adding a redundant branch in terms of reduction of the number of assembly modes and elimination of potential uncertainty configurations is also investigated. The addition of a redundant branch to the three-branch parallel manipulators effectively yields a four-branch manipulator class. Considered in particular is a 3-4 form of the manipulator where two branch ends meet at one point on the mobile platform and symmetric main-arm joint sensing and actuation (two sensed/actuated main-arm joints per branch) is utilized. The addition of such a branch is found to be not as effective for assembly mode and uncertainty elimination as redundant sensing/actuation of main-arm joints.

A calibration method for parallel manipulators is introduced which is based on the redundant joint displacement sensing and does not require a calibration fixture when all of the main-arm joints of the considered manipulators are sensed. The procedure is applied and shown to be effective for the calibration of a redesigned parallel hand controller.

A sensor fault detection scheme for fault tolerant operation of parallel manipulators is introduced. The presented forward displacement solutions are used to develop sensor failure safe solutions. The fault detection analysis of the calibrated hand controller is investigated. Data analysis is performed to examine the sources of algorithmic failure. It is concluded that high accuracy in the passive spherical branch end joints is required to facilitate fault detection.

The solutions are implemented in computer simulation and also in real-time operation of a six degree of freedom parallel hand controller.