We present a new paradigm for performing remote haptic-robot interactive operations. The new paradigm is anchored on an architecture that combines local autonomy with a high-level exchange strategy of reference input. This represents a departure from the conventional reliance on direct exchange of low-level control signals in a global feedback control system. The new approach establishes two local autonomous controllers acting on the robot and the haptic device, interfaced at a higher level via a dual-proxy model. The dual proxy is a passive bridge between the local autonomous controllers. It generates appropriate motion and force reference inputs that are consistent with the task physical interactions and the levels of autonomy. Its model is adjusted online with respect to exchanged position, contact, and environment geometry information. A key component in this methodology is the perception algorithm on the robot side, the force-space particle filter, designed to reliably estimate in real time the environment contact geometry. The series of simulations and physical experimental validations of the approach demonstrate the transparency and high fidelity in haptic-robot interaction and its inherent robustness to communication delays.

In the present paper, we first adopt explicit force control from general robotics and embed it into teleoperation systems to enhance the transparency by reducing the effect of the perceived inertia to the human operator and simultaneously improve contact perception. To ensure stability of the proposed teleoperation system considering time-delays, we propose a sequential design procedure based on time domain passivity approach. Experimental results of master-slave teleoperation system, based on KUKA light-weight-robots, for different values of delays are presented. Comparative analysis is conducted considering two existing approaches, namely 2-channel and 4-channel architecture based bilateral controllers, and its results clearly indicate significant improvement in force transparency owing to the proposed method. The proposed system is finally validated considering a real industrial assembly scenario.

When performing tasks in uncertain environments and around humans, robots are likely to collide unexpectedly with people or objects. In order to ensure safety, most approaches rely on collision avoidance and try to prevent any contact from happening, which may result in unnecessary interruption of a task that would be feasible in spite of the obstacle. On the one hand, when an unexpected contact occurs, a safe robot behavior is required. On the other hand, it might be interesting to exploit the contact instead of moving away from it. In this paper, we present a contact-driven approach for safe and interactive robot operation to react to unforeseen contact events. This approach offers the possibility to control the contact while minimizing its effects on the robot tasks. It relies exclusively on the robot model and proprioceptive sensors. It is tested in simulation and hardware experiments on a 7 degrees of freedom robot arm and shows a safe contact behavior that does not interfere with the task, and as little as possible with the robot posture requirements.

Direct force control of robots is challenging, particularly since the interaction with the environment can render the robot unstable. This paper presents the results of novel approaches for passivity-based stability for a particular direct force control method, namely explicit force control. A step-by-step procedure to passivate and stabilise the control loop is presented and it explains how Time Domain Passivity Approach, a passivity-based tool widely used in teleoperation and haptics has been extended and applied in explicit force control. The electrical circuit and network-port representations derived in the process allows the analytical evaluation of the system and can be applied in other control architectures as well. The stability methods are presented both qualitatively and quantitatively with simulations and hardware experiments. A discussion about the results obtained and the energy behavior is also provided. Results are promising and suggest that these methods can be used for stable and high-bandwidth force control of robotic manipulators.

This paper extends the previously proposed Explicit Force Controller based on Time Domain Passivity Approach. When using the classical passivity observer, we encounter an energy accumulation problem: if the system stays a long time in stable contact, energy is dissipated and the passivity observer builds up a large value. This causes the passivity controller to be triggered late after the interaction becomes unstable, so we lose the advantage of the passivity controller. In order to deal with this energy accumulation issue, we propose two new passivity observers that allow us to quickly detect potential instability despite the accumulated energy. We prove the theoretical validity of these new observers. In addition, we propose a more generalized way of implementing the passivity based explicit force controller on a multi-DoF manipulator, using a model for the robot and environment that includes sensor flexibility, and a hybrid position/force controller in the operational space framework. The proposed method is experimentally tested with KUKA IIWA, and the improved performance is verified.