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Industrial robots are often used for the simulation of satellites during on orbit servicing. In order to cover also the docking phase, both robots are equipped with force-torque sensors, and the measured forces and torques are taken to compute the desired motion of the position controlled robots. Since the system dynamics of robots and of free floating bodies obviously differ, for each robot we distinguish...
Compliance in robot mounted force/torque sensors is useful for soft mating of parts in many assembly tasks. Nevertheless, it generates nearly undamped oscillations when moving a heavy end-effector in free space. In this paper, input shaping control is investigated to damp such unwanted flexible modes. However, the conventional method presents a major drawback: To eliminate the oscillatory dynamics,...
Standard industrial controllers of robot arms define constraints on the velocity, the acceleration, and the jerk and abort execution in case any of them is violated. In addition to satisfying these constraints, the presented method tries to generate a trajectory that is path-accurate, i.e., that exactly tracks the 6-dof shape of the desired path in axis space. Furthermore, the computed trajectory...
Stopping the motion of industrial robots in response to warnings or unexpected sensor data is a special case of trajectory generation. In contrast to emergency stops, here the robot has to satisfy the limits of the acceleration and the jerk. In addition, during the deceleration the robot must follow the path accurately, i.e., the shape of the original path may not be left. This is usually done by...
Industrial robots often have to move with an accuracy of less than 1 mm at a speed of more than 1 m/s. Servoing of arbitrary paths therefore requires feedforward control using predictions of future timesteps of the desired motion. These predictions are obtained by camera images which allow the definition of current and future timesteps of the desired path. This is integrated in an architecture which...
A learning system is presented which uses feedforward control to improve the accuracy of standard position controlled robots. The method is executed on joint level since in this case there are less couplings than in the cartesian space. On the other side the main goal is to reduce the maximal deviation from a given cartesian path. This requires extended algorithms which are derived and examined using...
The paper considers an a priori given robot trajectory which has to be recomputed when online sensed information on the environment is available. Then the original trajectory is adapted in order to continue the so far commanded motion by the sensed geometric shape. The adapted trajectory has to comply with restrictions on velocity, acceleration and jerk. Furthermore it is desired to converge to the...
Position-based force control is presented, incorporating compliance in the robot joints and possibly in a force- / torque-sensor and/or the environment. First, the total compliance is identified. Then, in the control phase, the desired pose of the tool center point is computed from the force control error. Thus standard position control may be applied. This leads to an inherently stable control scheme,...
A different way of force control is presented, that is especially advantageous for position controlled robots. Instead of usual force control laws we rely on the well tuned position control loop and just use the force sensor to measure the target pose or to predict the desired trajectory. In combination with a compliant sensor we introduce an inherently stable framework of force control which almost...
Typical industrial assembly tasks require an accuracy that cannot be realized by only feedback control if a minimum speed is given by a conveyor. Feed-forward has proven to be advantageous, using predictions of the desired trajectory which will be computed from sensor values. These predictions are improved by a model based classification of the sensor data to typical scenarios. In contrast to linear...
Within assembly lines, wheel assembly to continuously conveyed car bodies is still executed by human workers using a device that compensates the weight of the wheel. This paper presents a solution in which a robot autonomously assembles and fixes the wheels. The approach uses a sensor-driven control strategy that compensates a possible temporal or spatial offset. Three types of sensors are proposed...
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