Design of gravity balancing leg orthosis using non-zero free length springs

For gait retraining of stroke victims, there is a need for rehabilitation devices, which can support the weight of leg during walking. Machines that gravity balances the leg are potentially useful as rehabilitation devices. This paper presents gravity balancing designs for two and three links planar chains using non-zero free length springs. Non-zero free length springs are those springs which have initial free length. These springs are cheaper, easily available and can be useful when complete weight balancing is not required. These designs are further optimized for spring connection points and parameters of the spring such as free length and stiffness to achieve greater balancing.