The human machine-interface is more important than ever in the field of exoskeletons. Current design approaches lack a way of systematically designing the ergonomics of exoskeletons. Methods with a more pro active approach to ergonomics have to be developed. This thesis extends existing methods by which self aligning mechanisms are created with a systematic approach. A synthesis method is proposed by which all possibilities are synthesized. These possibilities are then excluded based on kinematic requirements on the system. The remaining possibilities are optimized based on ergonomic guidelines to obtain a set of solutions from which the designer can make well founded design choices. A force-deflection analysis was performed on the resulting solutions. This proposed method is applied to a planar passive exoskeleton for the shoulder. The method was successfully applied by using the total link length, reachable workspace, distance to the body and singularity avoidance as objectives for the optimization. Stiffness was added to the joints to obtain the required force-deflection behavior. The resulting objective values were verified by means of a prototype. The test results showed to be within reasonable bounds to verify the method for the planar case. The force-deflection analysis showed results that can be achieved by linear springs. This has to be verified by additional tests. The proposed method can be used as a tool in future exoskeleton design and can be extended with additional objective functions and constraints and can be extended to the three dimensional case.