STOCHASTIC ERROR PROPAGATION IN ROBOT ARMS

Static error propagation in positioning robot arms has been extensivel y analyzed based on linearized error propagation models. These models are used for robot design and calibration. Most results were calculate d using normally distributed errors in the different robot joints and links. In reality not all joints and links errors are normally distrib uted, and a mix of suitable symmetric and nonsymmetric probability dis tributions should be used in the error propagation model. The paper pr esents the general model for propagating errors with different distrib utions applicable to any system whose model can be linearized. Numeric al examples are given for a general beta distribution of errors, and f or a mix of symmetric and nonsymmetric distributions. Within the work- volume, the different configurations that a robot arm may attain durin g its life span can be expressed by a probability distribution. The pa per includes the analysis of the effect of this distribution on the po sition error of the end-effector.