The serial link manipulators are most commonly used for industrial applications. The positional accuracy is an important specification for performance evaluation of a serial chain manipulator. The factors influencing the positional accuracy of serial link robotic manipulator includes joint clearances, and drive backlash. This paper presents method for evaluating the effect of joint error on positional accuracy of the robotic manipulator. Serial chain Two Revolute Joint (2R) planar manipulator is modeled to position the end effector in workspace. The inverse kinematic analysis under ideal joint provides the link properties for respective end effector location. Formulation for manipulator link properties under influence of the joint clearance is presented. Effect of drive backlash on positional accuracy of end effector is analyzed. Positional deviations at end effector positions over workspace are estimated. Maximum error under influence of backlash and clearances is estimated at all possible end effector positions.

Closed chain mechanisms are used as robotic manipulators with special features. A planar two-DOF closed loop mechanism provides desired position of an end effecter in a confined workspace with two input motions. Position of end effecter depends on various factors including joint clearance. Positional accuracy forms important parameter for kinematic analysis of mechanism. This paper presents simple approach for quantifying error due to joint clearance in a two-DOF mechanism. Generalized scheme for positional deviation with and without clearance at joint is presented. Orientation of clearance links for maximum positional error is identified. Error at various positions is quantified in relation with clearance link length. Computer programming is used as a tool to workout positional analysis of mechanism. Results show that error is independent of magnitude of clearance, however, a function of location of end effecter in workspace.

Many planar manipulators are composed of a basic four-bar mechanism. The output delivered by the mechanism deviates from desired one due to factors like link tolerances. The performance needs to be characterized for satisfactory application. This article presents investigation of mechanical error in four-bar mechanism with revolute joints (4R) under the influence of link tolerance. The classical partial derivative formulation (PDA) in uncertainty analysis technique is primarily used for estimating the mechanical error. The error estimation is carried out with proposed modification in PDA formulation. A geometric approach is also developed to estimate the mechanical error for 4R configuration. The mechanical error obtained through PDA is verified using geometric approach. The generalized formulation is demonstrated, and comparative estimation is presented. The methods and conclusions proposed herewith are adaptable for other planar configurations.

This paper presents the mechanical error estimation under the effects of link tolerances in a 3-degree-of-freedom (DoF) 3-RRS Spatial Parallel Manipulator (SPM). Position level kinematic analysis and workspace analysis in the form of reachable and orientation workspace are carried out initially. Then, the effect of link tolerances on individual link is studied at the position of mid-point and orientation of the movable platform. The corresponding mechanical errors are estimated. The effect of link tolerance variation is studied to know the pattern of mechanical error. The 3-D CAD model in SolidWorks is used to validate the results. The conclusions are drawn that lead to error minimization at the tolerance design stage.

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