Singularity conditions from a kinetostatic analysis of a new parallel robot for human balance and gait rehabilitation

• BALANCE robotic device is proposed for human balance and gait rehabilitation. • Analysis of a new parallel manipulator capable of providing BALANCE trajectories. • Presentation of a simpler approach for singularity identification. • Geometric characterization of the singularities for working mode selection. This paper presents a novel device for the rehabilitation of balance and gait functions in patients with neurological disorders. The device is composed of two sensorized footplates, one for each foot of the patient, which are driven by two identical 4-DOF parallel manipulators. The mobility and kinematic analyses of this new parallel manipulator are conducted for the first time, including the resolution of the inverse position problem and the formulation of the overall Jacobian matrix. Then, a simplification of the kinetostatic problem is proposed, which not only reduces the computational cost but also leads to a reduced matrix that enhances the singularity analysis process. Using this matrix and placing emphasis on the geometric interpretation of the singularity conditions, a thorough characterization of them is carried out, which has proven useful for the working mode selection and for visual verification of the rehabilitation trajectories proposed in the path planning process. The paper concludes with the presentation of a prototype intended to validate the usefulness of this device in the rehabilitation field.