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This paper focuses on online time optimal control of nonlinear systems. This is achieved by approximating the results of time optimal control problems (TOCP) with deep neural networks (DNN) depending on the initial and terminal system state. In general, solving a TOCP for nonlinear systems is a computationally challenging task. Especially in the context of time optimal nonlinear model predictive control...
This paper addresses the time‐optimal trajectory planning of a redundantly actuated parallel robot driven by series elastic actuators. Here, the actuation redundancy allows prestressing the elastic components of the drives and enables more degrees of freedom in the trajectory planning. To this end, a time‐optimal control problem is formulated that takes also the physical constraints into account,...
Redundantly actuated parallel kinematic manipulators (RA‐PKM) are ideal candidates in robotic applications combining dynamic performance with high accuracy. Actuation redundancy further allows for modulation of the end‐effector (EE) stiffness. A recent trend in robotics is the use of inherently compliant and elastic components, eventually leading to soft continuum robots, which shall provide tailored...
This contribution focuses on the optimal trajectory planning for a Segway model (inverted pendulum on two independently actuated wheels). Basis for this planning is the dynamical model for this under‐actuated, non‐holonomic multibody system. For the stabilization as well as the trajectory control, a partial input/output linearization is performed, where the orientation of the robot w.r.t. the horizontal...
Impact and the resulting contact forces can be determined by dynamic simulation once a validated model for the robot and of the contact area of the human is available. Methods for the identification of relevant geometric and dynamic parameters of the robot model are well established. While the experimental validation of constitutive models for human body contact is still topic of ongoing research,...
This contribution focuses on the dynamical modeling and control of a self‐balancing bicycle. The bicycle is equipped with two flywheels rotating at constant speed mounted via a hinge that is actuated by an additional motor and allows for rotation about the vertical axis. Due to the balance of angular momentum, a torque is generated around the axis perpendicular to the hinge and spinning axis, i.e...
This paper deals with time optimal path tracking along prescribed geometric paths for robotic systems, like computerized numerical control (CNC) machines. These machines are typically controlled by a low cost microcontroller computational unit (MCU). Such MCUs are commonly used in industrial applications but are limited in view of computational performance. In many cases, these robotic systems have...
A recent development for programming industrial robotic manipulators is the interactive teaching of task motions where a human operator physically guides the end‐effector of a robot. Admittance control schemes are used to this end. Since the operator is in direct contact with the robot, it must be ensured that the velocities of the robot are within a safe range at any time. Thus, in order to guarantee...
The worldwide population aging and hence the higher risk of age‐related diseases facilitates interest in robotic devices for rehabilitation and movement assistance. A major factor of a persons functional independence is the ability to perform the movement task of standing up from a chair, also known as sit‐to‐stand (STS) movement. This work focuses on the development of a passive, wearable knee orthosis...
Time‐optimal path following, i.e. moving a robot's end‐effector optimally along a specified geometric path, is a very important and well discussed problem in robotics. Nevertheless, most of the existing approaches concerning this topic neglect the speed dependency of torque constraints. The present paper presents a method for taking such constraints into account within a dynamic programming approach...
Due to their low weight robots with flexible links are ideal candidates for use in dynamically demanding applications. Since the main goal of the robot control is to achieve precise positioning, the damping of oscillations due to low stiffness is imperative. Furthermore classical PD motor position control is insufficient for vibration damping. This paper presents an approach using an eye‐in‐hand camera...
This paper discusses some dynamical aspects of a self‐balancing Inertia Wheel Cube (IWC). The acceleration and deceleration of actuated flywheels is used to stabilize the IWC when balancing on one of its corners, which is an unstable equilibrium position. The orientation as well as the rotational velocity of the device are measured by an inertial measurement unit (IMU). The equations of motions are...
Mechanism theory, synthesis and control of robots, rigid body dynamics, geometrically exact formulations of the kinematics of continua, structure preserving numerical integration methods, and in part geometric mechanics – they all have a common denominator, namely the theory of screws, for which Lie group theory forms the mathematical foundation. This paper is an attempt to provide a short survey...
This paper presents a method for the identification of inertia parameters of non‐holonomic omnidirectional (NHO) vehicles. NHO vehicles use several centered steerable standard wheels for their movement. They are omnidirectional in the sense that they are able to drive in each direction but may have to steer the wheels before starting the motion. A precise knowledge of the inertia parameters of such...
Nowadays robotic manipulators are considered to perform a wide range of tasks. Since robotic systems consisting of multiple manipulators are capable of handling a variety of tasks that cannot be executed by single manipulators, cooperation of multiple manipulators is becoming increasingly interesting in particular for industrial applications. The interaction with other manipulators, respectively the...
Passivity‐based control has exclusively been pursued for dynamical systems possessing energetic state functions that are quadratic in the generalized velocities. This assumption does not apply to many dynamical systems, for instance in electromechanics, thus passivity‐based control has not been established for these classes of systems. This contribution presents an augmented PD control scheme for...
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