Using a robust normalized gradient update law (known to those skilled in the art) for the linear-in-parameter inner-loop output equation, Equation 27, gives the electrical parameter estimate update law ##EQU16## for j=1, . . . , M, where ??e is a diagonal matrix of design gains, ??e and ??e are design parameters and ##EQU17## is a dead-zone function which improves robustness.