Volume 61, Issue 9

Based on models of human perception, this paper investigates the influence of artificial sensory feedback on prosthetic gait. A simple static neuromechanic model of a transfemoral prosthesis and amputee perception reveals possible effects during stance phase. To analyze swing phase, an observer model of the prosthesis is implemented using an Extended Kalman Filter. While standing, feedback of the Center of Pressure may improve perception, whereas during gait amputees do probably not profit from additional information. A clinical case study would have to reveal whether the theoretical analysis correctly determines the effects of feedback on amputee locomotion.

Functional electrical stimulation can be used to support the dorsiflexion of the foot during the swing phase of gait. Iterative learning control is employed to generate natural foot angle trajectories. In this article we consider early ground contact due to insufficient stimulation and study the resulting coupled dynamics of the error and the pass length. First, adequate theoretical concepts are discussed, which are then used for controller design. Finally, the achievable convergence properties are analyzed experimentally.

Active knee orthoses can be used to allow the elderly comfortable everyday living in their familiar environment. To actuate these devices, serial-elastic actuators (SEA) prove to be advantageous as their controllability in close contact to the user is better when compared to directly coupled geared DC motors. SEA, in addition, usually provide a better overall system power-to-weight ratio than fluidic actuators or direct drive electrodynamic actuators. In the following, the selection and the dimensioning of an SEA for an active knee orthosis, its control strategy using a state-space controller, and first experimental results as well as their relation to the state of the art are presented.

In this paper, a modeling approach and a control concept for a Hardware-in-the-Loop (HIL) test bench for ventricular assist devices are presented. The purpose of the HIL test bench is to simulate the pressures at the in- and outport of a ventricular assist device as given by the cardiovascular system of a patient. This enables testing of control algorithms for ventricular assist devices in an efficient and cost-saving manner. The modeling is performed using Lagrange’s equations. The control concept is based on PI- and LQR-control. The control concept is evaluated by transferring ventricular and arterial pressures generated by a simulation of the cardiovascular system to the HIL test bench.

To support the surgeon during opening of the skull in neurosurgery or of the sternum in cardiothoracic surgery, a semiautomatic, hand guided saw was developed. The cutting depth is automatically controlled on the basis of three different modalities (computed tomography, ultrasound, light). In addition to the general successful proof of general feasibility, the present paper provides the results of a detailed comparison of the different systems in combination with an analysis of the structural advantages and disadvantages and their individual optimization potential.