21 accepted papers
Model predictive control (MPC) has become increasingly popular for the control of robot manipulators due to its improved performance compared to instantaneous control approaches. However, tuning these controllers remains a considerable hurdle. To address this hurdle, we propose a practical MPC formu
Trajectory segmentation refers to dividing a trajectory into meaningful consecutive sub-trajectories. This paper focuses on trajectory segmentation for 3D rigid-body motions. Most segmentation approaches in the literature represent the body’s trajectory as a point trajectory, considering only its tr…
Trajectory optimization is a powerful tool for robot motion planning and control. State-of-the-art general-purpose nonlinear programming solvers are versatile, handle constraints effectively and provide a high numerical robustness, but they are slow because they do not fully exploit the optimal cont…
Learning from Demonstration (LfD) requires methodologies able to generalize tasks in new situations. This paper studies the use of virtual demonstrations to extend the extrapolation capabilities of probabilistic motion models such as the traPPCA method. Similarly to other LfD methods, traPPCA is abl…
In this work we present our results on dynamic visual servoing for the case of moving targets while also exploring the possibility of using such a controller for interaction with the environment. We illustrate the derivation of a feature space impedance controller for tracking a moving object as wel…
Constraint-based robot programming allows for implementing sensor-based skills that react to disturbances on the one hand, and composable skills that dynamically create and reconfigure complex robot behaviors on the other hand. In this letter, we address a class of problems where composing appropria
In this work, we propose a constraint-based reactive framework that allows an easy customization of assistive robotic systems to comply with the particular needs of users with different levels of mobility. This framework enables the specification of modular assistive reactive behaviors which can be
Variation in task requirements and operation in uncertain environments require robots that can continuously adapt their motions during execution. To do this successfully, the original motion characteristics must be preserved. This paper presents an approach for on-line adaptation of end-effector tra
This letter presents a method to sense motor torque of multirotors in steady state, without additional torque sensors by using the measured input voltage, throttle setting and rotational speed. Torque, rotational speed and current of a brushless direct current (BLDC) motor with electronic speed cont
This letter presents a framework for recognition and prediction of ongoing human motions. The predictions generated by this framework could be used in a controller for a robotic device, enabling the emergence of intuitive and predictable interactions between humans and a robotic collaborator. The fr
There is a high cost associated to the time and expertise required to program complex robot applications with high variability. This is one of the main barriers that inhibit the entry of robotic automation in small and medium-sized enterprises. To tackle the high level of task uncertainty associated…
In this paper, we aim to expedite the deployment of challenging manipulation tasks involving both motion and contact wrenches (forces and moments). To this end, we acquire motion and wrench signals from a small set of demonstrations using passive observation. To learn these tasks, we introduce Traje…
This paper introduces a constraint-based skill framework for programming robot applications. Existing skill frameworks allow application developers to reuse skills and compose them sequentially or in parallel. However, they typically assume that the skills are running independently and in a nominal…
This letter combines an combines an imitation learning approach with a model-based and constraint-based task specification and control methodology. Imitation learning provides an intuitive way for the end user to specify context of a new robot application without the need of traditional programming
When walking robots and exoskeletons make multiple independent contacts, the inverse dynamics problem requires additional knowledge about the contact forces and moments. To avoid measuring the contact forces and moments, many inverse dynamics controllers for walking robots optimize an objective such
The control of mechatronic systems can often be enhanced if realtime information on the derivatives of a signal is available. These derivatives are not always measurable by sensors and should be estimated. Simple numerical derivatives cannot be applied, due to noise on the measured signals. Several
Invariant representations of demonstrated motion trajectories provide context-independent motion models that can be used in motion recognition and generalization applications such as robot programming by demonstration. In practice, the use of invariant representations is still limited because their…
In programming by demonstration, generalization is necessary to apply demonstrated motions in novel situations. Many existing trajectory representations have poor generalization capabilities since they are built on trajectory coordinates that depend on the context in which the motion is recorded. In…
Accurate and reliable event prediction is imperative for supporting movement with an exoskeleton. Two events are important during a sit-to-stand movement: seat-off, the event at which the subject leaves the chair and start-of-assistance for hip and knee, the earliest time at which assistance may be
This paper presents an overview and comparison of minimal and complete rigid body motion trajectory descriptors, usable in applications like motion recognition and programming by demonstration. Motion trajectory descriptors are able to deal with potentially unwanted variations acting on the motion t…
An increasing number of robotic systems are using compliant actuators in which springs are placed in series with the actuator. The need for identification procedures tailored to these systems is consequently rising. When measurements of both the link side and the motor side of the spring are availab…