A servo-controller is developed for a three joint manipulator. The servo-controller consists of a dead beat controller and an on-line parameter estimator. The dead beat controller is implemented in four steps. A piecewise linear model is calculated on line. Simultaneous diagonalization of the stiffness and inertia matrices is performed after linearization. A control vector for the linearized, diagonalized system is generated at a faster rate. The control vector is transformed from the diagonalized mode to the real mode via multiplication by a transformation matrix. The parameter estimator is a least' squares estimator designed to estimate the stiffness parameters in the diagonalized mode. The parameter estimator iteratively estimates the eigenvectors and eigenvalues associated with the stiffness parameters. The parameter estimator converges too slowly to meet the design requirements. The controller, however, provides an acceptable tracking error* and is robust enough to use without the parameter estimator.