disturbances varied from 0 to 30 Hz with amplitudes
varying from 0 to 30 Nm, and the disturbances have been
injected at the would point where the user exercises forces
onto the robot. For this simulation, the saturation of the
motors has been set to 25 Nm.
A series of simulation studies leads to the result that the
position error stays small while the velocity error varies with
the frequency and amplitude of the disturbance (Fig. 9).
3.2 Functional tests with healthy subjects
Within the tests with healthy subjects, the ROM, the control
and the overall functionality have been validated
(Table 5). These tests included 20 min’ mobilisation therapy
and 40 min’ game therapy.
3.3 Pilot study with patients
A pilot study was carried out to validate the patient comfort
and handling, i.e. whether the robot is adjustable to different
patient sizes, whether the cuffs are comfortable for
the patients, and whether the patients are able to perform
the movement tasks. Furthermore, the patient acceptance
and motivation were interrogated.
Using the same protocol as for healthy subjects, the
robot has been tested with 11 patients for a cumulative
duration of more than 76 h. The robot could easily
accommodate subjects with body sizes between 155 and
192 cm. The fixation of a patient in the robot takes
approximately 5 min.
Figure 10 shows an example for a trajectory recorded by
a therapist and the resulting trajectory after applying the
minimum jerk approach. Note that the extreme values of
both trajectories correspond with each other.
Figure 11 shows the results of the game therapy with
two different hemiplegic patients. A ball has been displayed
falling down on the graphical display. The patient
had to catch it by moving the virtual hand (Fig. 6, upper
right). Subject A was able to catch the ball mostly without
any robot support. The robot assisted patient B by pushing
the patient with the force Fxref towards the ball (Fig. 11), if
the patient was not able to catch the ball himself (cf. Chapt.
2.9). Note that the robot support is always delayed relatively
to the change in the horizontal ball position. In this