An unenergised aid to standing up, sitting down and lying down for partially disabled people has been optimised and a half size kinematic model made. Various facilities such as a foot rest, leg rest, arm rest and knee rest are also provided. The patient is lifted and placed in the desired standing and lying positions. An improved Rosenbrock optimisation technique using a penalty function approach is used to determine the optimum dimensions of the various links used in the chair mechanism. A general computer program has been developed to ascertain new dimensions of the mechanism for different input-output functional relationships.