This paper presents a novel approach for time-optimal path parameterization based on reachability analysis for robotic systems with viscous friction in the dynamics and jerk constraints. The main step of the method is the backward propagation of controllable sets through a linear second-order system. In order to avoid the unbounded growth of the number of constraints, the sets are approximated by a ray shooting algorithm. Using a convex relaxation, the required set expansion can be solved with second-order cone programming. Evaluation results for a 6-degree of freedom (DOF) robot arm highlight the advantages of the method for computing jerk-limited trajectories.

This paper presents a time-optimal path parameterization (TOPP) method for cooperative multi-arm robotic systems (MARS) manipulating heavy objects with third-order constraints that include jerk, torque rate and wrench rate limits. The method is based on a problem reformulation as a sequential linear program and provides a unified planning approach that is faster than previous convex optimization techniques. The equivalence to a reachability-based TOPP is shown and simulation results for a cooperative MARS consisting of two 7 degree of freedom (DOF) robots and a tightly grasped object with 6 DOFs are provided.

This paper presents a new control scheme for cooperative dual-arm robots manipulating heavy objects. The proposed method uses the full dynamical model of the kinematically coupled robot system and builds on a hierarchical quadratic programming (HQP) formulation to enforce dynamical inequality constraints such as joint torques or internal loads. This ensures optimal tracking of an object trajectory, while additional objectives with lower priority are optimized on the prior solution space. Therefore, the redundancy of the inherent load distribution problem between the two arms can be eliminated. With this approach, higher object loads can be manipulated compared to non-optimized methods. Simulations with a 14 degree of freedom (dof) dual-arm robotic system demonstrate the effectiveness of the proposed control method. The real-time feasibility is guaranteed with an average computation time of less than 0.35 milliseconds at a control rate of 1 kilohertz.

This article presents the concept of model predictive interaction control (MPIC) as a generic, flexible, and comprehensive approach for robotic manipulation tasks. MPIC is based on the repetitive solution of an optimal control problem that includes a robot model for motion prediction as well as an interaction model for force prediction. In order to handle both elastic and rigid contact situations, a cascaded approach with low-level PD control is adopted, which allows to combine the linear-elastic environment model and the limited controller stiffness. Due to its flexibility, MPIC can be favorably used for realizing the elementary manipulation primitives (MP) within a hierarchical task planning framework, where each MP corresponds to a particular parameterization of the cost function and the constraints. The control methodology and the manipulation approach are evaluated in simulations and experiments using a 7-degree-of-freedom industrial robot.

The development of modern sensitive lightweight robots allows the use of robot arms in numerous new scenarios. Especially in applications where interaction between the robot and an object is desired, e.g. in assembly, conventional purely position-controlled robots fail. Former research has focused, among others, on control methods that center on robot-environment interaction. However, these methods often consider only separate scenarios, as for example a pure force control scenario. The present paper aims to address this drawback and proposes a control framework for robot-environment interaction that allows a wide range of possible interaction types. At the same time, the approach can be used for setpoint generation of position-controlled robot arms, where no interaction takes place. Thus, switching between different controller types for specific interaction kinds is not necessary. This versatility is achieved by a model predictive control-based framework which allows trajectory following control of joint or end-effector position as well as of forces for compliant or rigid robot-environment interactions. For this purpose, the robot motion is predicted by an approximated dynamic model and the force behavior by an interaction model. The characteristics of the approach are discussed on the basis of two scenarios on a lightweight robot.

This paper addresses the optimization-based planning of collision-free motions for a dual-arm robot with kinematic constraints. Such problems arise, for example, when the robot has to move an object with both arms, whereby the two arms and the gripped object form a closed kinematic chain. Such constrained problems are hard to solve with sampling-based planners, because the probability that a random sample satisfies the closure constraint is practically zero. In contrast, the solution of optimization problems with equality constraints is a well-understood field of research. This paper formulates the motion planning task as optimization problem and proposes a numerical solution using the augmented Lagrangian method for handling constraints. The planner is compared to RRTs, CHOMP and TrajOpt on a set of randomly generated problems for a dual-arm robot with twelve degrees of freedom highlighting the advantages of optimization-based planning.