Bicycle for paraplegics

The cycle-wheelchair allows paraplegics to move a cycle powered by their own muscle force. The paralyzed leg muscles are artificially activated by means of functional electrical stimulation with surface electrodes. First tests with paraplegic test persons have shown that start up as well as unassisted movement is possible with the cycle- wheelchair. Description of the project: A paralyzed muscle, whose neural connection to the central nervous system is interrupted, can be artificially activated by functional electrical stimulation (FES). In an interdisciplinary FWF (Austrian Science Foundation) project, which was carried out at the Vienna University of Technology (Institute of Mechanics, Institute of Machine Elements) in cooperation with the Vienna University (Department of Biomedical Technics and Physics) and the Wilhelminenspital Vienna (Department of Physical Medicine), a cycle-wheelchair was developed, which is driven by paraplegics whose leg muscles are artificially activated by means of FES. Pedaling by means of FES: To realize the pedaling movement by means of FES the force generated by the muscles has to be converted into drive torque. An optimized pedal path was developed which is different to the usual circular path and allows conversion of the muscle forces to drive torque with higher efficiency. The stimulation intervals of the single muscles are adjusted by the electronic control so that each of the three muscle groups (Quadriceps, Hamstrings, Gluteus Maximus) is active in that part of the crank rotation where positive drive torque is generated. Cycle geometry: With the cycle-attachment, including the front wheel and components of the drive mechanism, commercially available wheelchairs can be converted to cycle-wheelchairs. By mounting two fixing rails under the seat of the wheelchair the cycle-attachment can easily be mounted and dismounted, what simplifies transport as well. An auxiliary motor generates additional drive torque for getting over gradients or if the muscle forces are too low e.g. due to fatigue. The applied pedal forces and the knee angles are continously measured and checked. If the forces get too high or one knee angle shows overstretching the stimulation is immediately switched off and the motor to idling to avoid injuries. Motivation: The FES training has a number of physiological benefits for the patients: muscle atrophy is reduced, circulation is increased and the development of pressure ulcus avoided, the cardiovascular system is trained. Regular (daily) training is necessary for effectiveness of the FES-training. In this respect the cycle-wheelchair will be especially helpful since it combines the physiological benefits of the FES-training with the psychological incentive of independent locomotion.