Sylvain Miossec

Planning contact points for humanoid robots

We present a planner for underactuated hyper-redundant robots, such as humanoid robots, for which the movement can only be initiated by taking contacts with the environment. We synthesize our previous work on the subject and go further into details to give an in-depth description of the contact planning problem and the mechanisms of our contact planner. We highlight the structure of the problem with a simple example, present the contact space and the heuristics we use for planning, and explain thoroughly the implementation of the different parts of the planner. Finally we give examples of planning results for complex scenarios with the humanoid robot HRP-2.

A humanoid walking pattern generator for sole design optimization

We devised a new walking pattern generator based on a minimization of the energy consumption that offers the necessary parameters to be used in flexible sole design problems. This pattern generator is implemented in two sets of experiments implying the HRP-2 humanoid robot: walking with different weighting between (i) the center of mass forces, and (ii) torques applied at the ankle joint. We also considered two types of feet: the HRP-2 built-in flexible ankle, and our proposed solution that keeps the ankle-to-foot without flexibility and add instead a flexible sole. The latter shows several benefits that are discussed.

A Strictly Convex Hull for Computing Proximity Distances With Continuous Gradients

We propose a new bounding volume that achieves a tunable strict convexity of a given convex hull. This geometric operator is named sphere-tori-patches bounding volume (STP-BV), which is the acronym for the bounding volume made of patches of spheres and tori. The strict convexity of STP-BV guarantees a unique pair of witness points and at least C1 continuity of the distance function resulting from a proximity query with another convex shape. Subsequently, the gradient of the distance function is continuous. This is useful for integrating distance as a constraint in robotic motion planners or controllers using smooth optimization techniques. For the sake of completeness, we compare performance in smooth and nonsmooth optimization with examples of growing complexity when involving distance queries between pairs of convex shapes.

Humanoid walking with compliant soles using a deformation estimator

We study the effect of soft (i.e. compliant) soles in humanoid walking. Adding compliance at the foot sole is important for shock absorption during touchdown and to better cast the ground roughness. But, subsequent deformation needs to be considered in the attitude stabilization. We propose a sole deformation estimator used in the controller design, to ensure that the desired ZMP for stability requirement is fulfilled. We performed two comparison experiments on the HRP-4 humanoid robot with/without the estimator. Experiments showed how the estimator enhances the ZMP stabilization during walking and prevents the robot from falling down.

Robotic co-manipulation with 6 DoF admittance control: Application to patient positioning in proton-therapy

The paper focuses on controlling by hand a robot carrying a patient lying down on a “couch top” located at the extremity of the end-effector. The Orion prototype, is a six Degree-of-Freedom (DoF) robotic system. The control of the robot is achieved through a home-made co-manipulated haptic device located under the couch top and operated by a paramedical assistant. This device enables the operator to move the couch top, on which the patient lies down, and within an identified operational safety space. The 6 DoF admittance control algorithm is implemented on this new robotic platform. An experimental validation has been carried out to validate the co-manipulation control of the robot. The adaptable admittance parameters have been tuned on several experiments in order to observe the mass-spring-damper equivalent behaviour and demonstrate the validity of the implemented admittance algorithm.

Optimized humanoid walking with soft soles

In order to control more efficiently the feet-ground interaction of humanoid robots during walking, we investigate adding outer soft (i.e. compliant) soles to the feet. The deformation subsequent to the contact of the soles with the ground is taken into account using a new walking pattern generator and deformation estimator. This novel humanoid walking approach ensures that the desired zero moment point for stability requirement is fulfilled. We validate our new controller using the HRP-4 humanoid robot performing walking experiments with and without the estimator. Also, to test the robustness of our approach and to obtain low-energy walking, we performed different walking motions.

Design of optimized soft soles for humanoid robots

We describe a methodology to design foot soles for a humanoid robot given walking gait parameters (i.e. given center-of-mass and zero-moment-point trajectories). In order to obtain an optimized compliant sole, we devised a shape optimization framework which takes –among other inputs, an initial rough (simplified) shape of the sole and refines it through successive optimization steps under additional constraints and a cost function. The shape is optimized based on the simulation of the sole deformation during an entire walking step, taking time dependent input of the walking pattern generator into account. Our shape optimization framework is able to minimize the impact of the foot with the ground during the heel-strike phase and to limit foot rotation in case of perturbations. Indeed, low foot rotation enforces a vertical posture and secures the balance of the humanoid robot. Moreover, weight restriction (formulated as a constraint on the sole volume) is added to our optimization problem.

Torque Collision Detection with Experimental Validation for Protontherapy Positioning Robot

During a robotised protontherapy treatment, clinician, paramedical assistants and medical devices (stepladder, trolley, etc.) often enter the robots workspace. To overcome safety problems, a precise and reliable collision detection technique has been implemented on the LEONI Patient Positioning System (PPS) named Orion PT. This method provides safety not only for persons who are working within the robot workspace but also for environment and for the robot itself. In fact, this technique consists in two phases: to detect collisions when they occur, then to stop the robot immediately. Therefore, a classical and reliable approach based on pre-calculated torque collision detection, has been used. However, contrary to most of recent research works, which focus on lightweight robots, the method described in this paper is adapted to heavy and high inertia serial robot. Moreover a modelling and identification phase of gears kinematic irregularity has been studied. Finally, an experimental validation with force measurement during a real scenario has been carried out to demonstrate the performance of the porposed approach.

Dimensional Optimization of a Two-Arm Robot for Single-Site Surgery Operations

Unlike open surgery, minimally invasive surgery (MIS) involves small incisions through which instruments are passed to perform surgery. This technique is preferred since it reduces postoperative pain and recovery time. Laparoendoscopic single-site (LESS) surgery is the next step in MIS; a single incision is created instead of multiple access points for allowing the instruments to enter the peritoneal cavity. However, such minimally invasive techniques force the surgeon to perform more complex movements, hence the interest to use robotic systems. Design of robots for LESS is challenging to avoid collisions, reduce weight, and improve compactness while respecting the technical requirements (minimum forces, velocities). In this paper, we present the dimensional synthesis of a two-arm robot used for LESS. Each arm has a 2R-R-R architecture with link lengths optimized to respect the workspace constraints and maximize compactness while improving the performance in terms of forces and velocities (kinetostatic properties).Copyright