The dimensions of the planar-linkag

The dimensions of the planar-linkage mechanism have been calculated using the kinematic model, which has allowed reaching a balance between the achieved ROM and the size of the actuators (30 mm stroke). More precisely, the index finger can perform a maximum hyperextension movement of 8° and -5° at the MCP[] and PIP [] angles and a maximum flexion of −63° and -76° at the MCP[] and PIP [] joints, respectively. The obtained ROM is smaller than the natural ROM of the fingers (Table 1). However, it allows hyperextension (Fig. 16, Fig. 19) and it is greater than the one reported in other related works. For example, the MCP angle of HoH varies from 0° to −55° with an actuator of 50 mm stroke, not allowing the hyperextension movement, which is essential for the treatment of people who experience flexor spasticity.This result confirms the validity of our underactuated design to achieve both closing (flexion) and maximum opening (hyperextension) movements of the fingers. This feature is very useful for many stroke patients suffering from hand spasticity, since it allows rehabilitation tasks in which the exoskeleton helps to open and extend the fingers, thus facilitating the recovery of the spastic hand. In particular, the following actions can be performed: