A pneumatic linear actuator is presented and evaluated. Designed to operate in demanding environments such as MRI, it is developed to be used with two motion control modes: 1) a step-by-step mode with tooth-based gripping to ensure precision, 2) a continuous mode available locally for fine positioning. The actuator can also be disengaged to enable direct handling by an operator, for example for comanipulation. The design is presented. A prototype, developed in the medical context, is implemented and characterized. A specific step-by-step control sequence is then elaborated based on its characterization. Testing of the dual-mode actuation is finally described. The complementarity between the two motion modes and possible adaptations of the original design are discussed.

Bilateral teleoperation under rate mode is known to be a difficult problem in terms of stability, especially when the slave manipulator interacts with a time-varying environment. This paper presents an energy based variable admittance control approach, whose principle combines the monitoring and the regulation of the energy exchanges with a passivity tank. It allows stable interactions with force feedback for any desired inertia, damping and stiffness parameters. Experiments are conducted to assess the efficiency of the proposed approach using an experimental setup with a variable stiffness environment. The obtained results illustrate the ability of the proposed strategy to stabilize a system otherwise unstable, with little effect on the transparency of the teleoperation system.

In this paper, an active compliant revolute joint actuated by hydraulic energy is developed. The joint is made of polymer for integration in medical robotic systems, even in a challenging environment such as Magnetic Resonance Imaging (MRI). The use of multimaterial additive manufacturing allows us to develop two original aspects. First, a new seal design is proposed to build miniature hydraulic cylinders embedded in the active joint, with low level of friction. Second, a rack-and-pinion mechanism is being integrated to a compliant revolute joint to obtain a high level of compactness. Design and experimental assessment of the hydraulic cylinder and the compliant joint with embedded rack-and-pinion are presented, as well as an illustration in the context of needle manipulation with passive teleoperation.

Surgeons performing laparoscopic surgery experience distortion when perceiving the stiffness of a patient's tissues. This is due to the lever effect induced by the introduction of instruments in their patient's body through a fulcrum. To address this problem, we propose to use the comanipulation paradigm. A robotic device is connected to the handle of the instrument while simultaneously being held by the surgeon. This device applies a force on the handle that reflects the force measured at the tool tip, with a gain that depends on the lever ratio. The implementation of this method is presented on an experimental setup and a preliminary assessment experiment is presented.

This paper presents a new actuator designed to produce forces under short stroke displacements. Two variants of the prototype have been manufactured using Multi-Material Additive Manufacturing process, based on a flexible origami-inspired architecture. The structure consists of an airtight chamber constituted by rigid plates combined with flexible hinges and surfaces in order to allow the generation of motion. We propose several insights on integration issues such as limited material resistance and maximum range of motion. Both versions of the prototype are then tested to assess their performances for single strokes and cyclic loading.

The design of intrinsically safe systems is an important issue in the development of physical human-robot interactions, in particular in the medical field. In this paper, we explore a new approach, motivated by a medical robotic application framework. The system is statically balanced, in any configuration. Its actuation results from a controllable modification of the balancing. This notably limits the interaction forces between the robot and its environment, but yet authorizes important features like accurate positioning or tracking while in contact, which are key characteristics for the application. In this paper, the robotic device principle is introduced, together with its original actuation, which is developed and experimentally assessed for a one DOF system. Capabilities such as trajectory tracking in the free space, reaction to unexpected collision and tracking of a moving environment are reported. The generalization to more DOF, as required to complete medical tasks, is also discussed.

In this paper, we focus on the technology issues to be solved to develop a cable-driven robot compatible with Magnetic Resonance Imaging constraints. This study is based on the design of a new compact cable-driven manipulator with remote actuators, initially developed for prostate interventions. One of the originalities of the system is to use an instrumented structure to evaluate the cable tensions and lengths in order to perform an adequate control. The sensors assessment has been experimentally achieved and the necessity to introduce a new control strategy using the developed sensors has been demonstrated.

In this paper, we study a class of one degree-of-freedom mechanisms in order to design linear haptic interfaces. They allow to perform straight line motions with only revolute joints, thus limiting the friction that characterizes linear bearings. We particularly describe the characteristics of these systems and their good properties to design haptic displays: parallel architecture, very good linearity, good use of the actuator torque. The Hoeken's mechanism which has the best characteristics to build a direct drive general purpose haptic display is selected. We present the fabricated prototype and its evaluation in terms of bandwidth, Coulomb friction and apparent mass.

This paper addresses the influence of human operators on telemanipulators bilateral control. A method to deal with the user variability is proposed, based on the auto-tuning of the force controller at the master side. First, the approach is evaluated experimentally with a group of users in the context of nonlinear interactions with soft tissues, showing very good tracking performances, for both force and position. Second, a robustness analysis is presented that allows to prove the stability of the system for large variations of the behavior of both the environment and the user. This analysis is based on an original uncertain model of the user.

The commercial development of haptic devices is very promising. Existing systems are often 6-degree-of-freedom mechanisms equipped with a stylus that acts as a tool. They exhibit force feedback for 3 or 6 degrees of freedom of their end-effector, depending on whether only forces or both forces and torques are rendered. Some planar devices are also used but oddly, one-degree-of-freedom linear haptic devices are quite rare. This lack can probably be explained by the necessary mechanical transformations that are required to achieve linear motions with rotary motors. In this paper, we review several possible structures and present the design of a new one-degree-of-freedom linear haptic device with a limited number of joints and a compact design, compatible with rotary actuation. We evaluate this device in the telemanipulation context.