Piotr Sauer

Application of a disturbance-rejection controller for robotic-enhanced limb rehabilitation trainings

The paper presents an application of a special case of an Active Disturbance Rejection Controller (ADRC) in governing a proper realization of basic limb rehabilitation trainings. The experimental study is performed on a model of a flexible joint manipulator, whose behavior resembles a real robotic rehabilitation device. The multidimensional character of the considered assisting mechanism makes it a nontrivial modeling and control problem. However, by the use of the ADRC approach, the modeling uncertainty in the plant is partially decoupled from the system, which increases the robustness of the whole control framework against both internal and external disturbances.

Active Disturbance Rejection Control for a Flexible-Joint Manipulator

This paper focuses on experimental verification of Active Disturbance Rejection Control (ADRC) on a one-link flexible-joint manipulator. The complexity of the considered system limits the ease of modeling and thus the performance of model-based control methods. ADRC is proposed in this research as an alternative to these techniques. It uses a disturbance observer to actively compensate the effects of perturbations acting on the system. A set of experiments was conducted in order to examine the robustness of the proposed control framework. The results obtained show that the ADRC method managed to stay robust against nonlinear behavior of the flexible-joint system as well as its dynamics parameters variations.

Study on possible control algorithms for lower limb rehabilitation system

In this paper, one of the possibilities of introduction of variable stiffness in a rehabilitation manipulator for lower limbs, is described. Mechanical design and working principle of a proposed system are presented. The following control algorithms for manipulators with flexible joints are suggested: the position control and the active impedance control. The tracking performance is experimentally studied for sinusoidal and polynomial reference trajectories. Obtained results confirm that both control strategies are suitable for controlling a rehabilitation manipulator with changeable stiffness.

Telerobotic simulator in minimal invasive surgery

This paper presents the concept of multi-level control system for minimal invasive surgery. The overall system is based on Staubli robot which plays the role of a robotic assistant for surgeons in laparoscopic cholecystectomy. The desired movement of the end effector is obtained by a movement of a joystick. In the paper, we present two simulation programs for the control of the Staubli RX60 robot which has been used as the robot assistant.

Ankle Robot for People with Drop Foot – Case Study

Walking ability, though important for a quality of life and participation in social and economic life, can be adversely affected by neurological disorders such as spinal cord injury, stroke or traumatic brain injury. The main goal of rehabilitation is to maximize motor performance and minimize functional deficits [4]. This requires a patient to practice repetitive motion, specifically using the muscles affected by neurological injury. In traditional rehabilitation, one or more therapists assist and encourage the patient through a number of repetitive exercises. Nowadays in a rehabilitation, mechanical systems (robots) are used to replace or assist the lost functions of human extremities and an attempt will be made to present them in more precise terms than hitherto.

A New Control Algorithm for Manipulators with Joint Flexibility

The new industrial robot is equipped with gear-boxes such as harmonic drives, which introduce elastic deformations at the joints. These deformations are regarded a source of problems, especially when accurate trajectory tracking of high sensitivity to end-effector forces is mandatory. It is shown that the joint elasticity should be taken into account in modeling a robotic manipulator and designing a control algorithm. If we assume that the elasticity may be modeled as a linear spring, we obtain a dynamic model which is twice of the order of the model of the same robot with rigid joints. In this case the design of a control algorithm is a difficult task. If dynamic parameters are not known exactly, adaptive control laws must be designed to guarantee stabilization or tracking. Control of a system with uncertain elements has been discussed in the robotics literature [1], [4], [6], [8]. In this paper, we consider an adaptive tracking controller for a manipulator with only revolute joint. This algorithm is an extension of the controller proposed by Loria and Ortega [9]. We have assumed that the model in [9] has in addition dynamic friction components on both link and motor sides. We have incorporated a harmonic drive into our system. The construction of this controller is based on Lyapunov theory [1], [2], [5], [12]. We assume that link and motor positions are available for measurements. Under these assumptions we propose a semiglobal adaptive tracking control algorithm. The paper is organized as follows. The mathematical description of the robot model and the control algorithm are described in Section 11.2. The concluding remarks are given in Section 11.3.

The robot assistant system for surgeon in laparoscopic interventions

This paper presents a concept of multi-level control system for minimal invasive surgery (MIS). The overall system is based on the Staubli robot which plays a role of a robotic assistant for surgeons in laparoscopic cholecystectomy. The desired movement of the end effector is obtained by a movement of a joystick or commands from the speech recognition system. In this paper, we present experimental results of control of the Staubli RX60 robot which has been used as the robot assistant. The system is named ASYSTANT.

Automatic determination of knee kinematics for lower limb rehabilitation manipulator design

This paper presents a fully automatic algorithm evaluating the knee joint kinematics on the basis of X-ray images. The practical instantaneous center of rotation (ICR) path acts as the main feature of interest. The X-ray images taken from unhealthy child subject while knee flexion, are used as an input data. A clear description of each step of the procedure is provided in the paper, i.e. the image preprocessing, morphological operations, object labeling, image stabilization, determination of bone landmarks, and calculation of ICR. The output information can be used as a basis in the design stage of lower limb rehabilitation manipulator.

A New Control Algorithm for Robot with Joint Flexibility

This paper considers a new control algorithm for robot with elastic joints. The proposed algorithm requires only position signals measurements. This algorithm is an extension of the control algorithm proposed by Loria and Ortega in [10]. We have assumed that model in [10] has in addition dynamic friction components on both link and motor sides. We have incorporated harmonic drives into our system. We have developed for the proposed model of manipulator an adaptive version of the control algorithm based on Lyapunov stability theory. This algorithm ensures that the tracking error posses desirable convergence property: semiglobal convergence to an arbitrarily small neighbourhood of zero in the presence of bounded disturbance.

ASYSTENT - Control System of a Manipulator for Keyhole Surgery

In this paper, we present control system which is named “Multi-level Control System of a Manipulator for Minimally Invasive Surgery (MIS)”. The overall system is based on the Staubli robot RX60 which plays a role of a robotic assistant for surgeons in laparoscopic cholecystectomy. The desired displacements of the end of the laparoscope is obtained by a movement of a joystick or commends from the speech recognition system. In this paper simulation applications and experimental results are presented.