A novel kinematically redundant ($6+3$) -DoF parallel robot is presented in this paper. Three identical 3-DoF RU/2-RUS legs are attached to a configurable platform through spherical joints. With the selected leg mechanism, the motors are mounted at the base, reducing the reflected inertia. The robot is intended to be actuated with direct-drive motors in order to perform intuitive physical human-robot interaction. The design of the leg mechanism maximizes the workspace in which the end-effector of the leg can have a 2g acceleration in all directions. All singularities of the leg mechanism are identified under a simplifying assumption. A CAD model of the (6+3)-DoF robot is presented in order to illustrate the preliminary design of the robot.

This paper presents reorientation manoeuvres applied to an omnidirectional wheeled robot for impact mitigation during short falls. The proposed robot architecture aims to build upon recent innovations in reorientation robots to attain fast, multi-axis reorientation. Indeed, the use of omnidirectional wheels allows for simplifications to be made with respect to previous mobile robot architectures that make the proposed architecture more efficient for free fall reorientation, while still maintaining free roaming capabilities. To test these improvements, a prototype is built and a free roam and two free fall demonstrations are completed. On the one hand, the free roam demonstration validates that translation along both horizontal axes and rotation about the yaw axis are achieved with the presented prototype. On the other hand, the first free fall demonstration shows that a worst case scenario of a 180-degree reorientation about one axis can be completed in just under 0.45 seconds (one-metre fall) and the second free fall demonstration validates that the prototype is capable of simultaneous reorientation about both the roll and pitch axes. Therefore, the fast, multi-axis reorientation capabilities of the developed prototype are verified.

This article provides a general framework for the use of low-impedance displacement sensors mounted on the links of a serial robot to provide an intuitive physical human–robot interaction. A general formulation is developed to handle the motion guidance problem, i.e., the mapping of the measured motion of the sensors into the required robot joint motions to provide intuitive responsiveness. The formulation is general and can be applied to any architecture of serial robot with any number of displacement sensors each having an arbitrary number of degrees of freedom. Then, the design of a novel three-degree-of-freedom low-impedance displacement sensor is presented as a particularly effective instantiation of the general concept. Partial force balancing is used to reduce the required elastic return action, thereby ensuring the low impedance of the interaction. A prototype of a three-degree-of-freedom displacement sensor is then introduced. Two such sensors are mounted on the links of a custom-built five-degree-of-freedom robot in order to demonstrate the proposed approach. Experimental results are provided and comparisons with other collaborative robots are given. It is shown that the proposed sensors and motion guidance approach yield very intuitive low-impedance interaction involving very low interaction forces.

A novel backdrivable 3-[R(RR-RRR)SR] kinematically redundant (6+3)-degree-of-freedom (DOF) spatial hybrid parallel robot with revolute actuators is proposed for low-impedance physical human–robot interaction. The kinematic model is developed based on the constraint conditions of the robot. It is shown that the type II (parallel) singularities can be completely avoided, thereby yielding a very large translational and orientational workspace. A workspace analysis is presented in order to demonstrate the capabilities of the robot. Mechanisms are then introduced to use the redundant DOF of the robot to operate a gripper with the robot actuators, which are mounted on or close to the base, thus reducing the inertia of the moving parts. The architecture of the robot makes it possible to use direct drive motors, thereby making the robot easily backdrivable and allowing the use of a very simple and effective controller. A prototype of the robot is then designed and built and the large workspace of the robot as well as the effortless physical human–robot interaction are demonstrated. The controller of the robot is then described, including a position control mode and a control mode for physical interaction, which does not require the use of a force/torque sensor or joint torque sensors. Because of its backdrivability and low moving inertia, the robot is particularly well-suited for physical human–robot interaction, as demonstrated in the accompanying videos.

This paper investigates the design of a three-degree-of-freedom rotational inertia generator using the gyroscopic effect to provide ungrounded torque feedback. It uses a rotating mass in order to influence the torques needed to move the device, creating a perceived inertia. The dynamic model and the control law of the device are derived, along with those of a comparable concept using three flywheels instead of a gyroscope. Both models are then validated through simulations. Further simulations are conducted to establish motor torque and velocity requirements, and the gyroscopic concept is identified as having the less demanding requirements. The mechatronic design of a prototype of an inertia generator is presented, along with modifications to the dynamic model. Preliminary experimental validations are conducted. As the prototype faces instability issues when using the flywheels at high velocities, they are conducted using 0 RPM initial velocities. The results confirm that it is possible to both reduce and increase the rendered inertia even with current limitations. Finally, improvements for a second version of the prototype are discussed.

This paper presents a novel sensing approach for the physical interaction between a human user and a serial robotic arm. The approach is inspired from the concept of macro-mini robot architecture. The framework is developed for a general multi-degree-of-freedom serial robot and a corresponding impedance control scheme is proposed. In order to illustrate the concept, a five-degree-of-freedom robotic arm was built as well as a six-degree-of-freedom low-impedance sensing device that is used to control the robot. Experimental results are provided.

This paper introduces a novel four-degree-of-freedom (4-DOF) parallel mechanism having 3 translational DOFs and 1 rotational DOF. The mechanism comprises 2 sets of parallelogram linkages, which constrain two of the rotational DOFs of the mechanism. An interesting feature of the mechanism is that it can be driven using 4 parallel sliders mounted on its base. As a result, one of the translational DOFs can be infinitely large. Also, the architecture of the mechanism provides a large rotational DOF in one direction. The kinematic equations of the mechanism are derived and the Jacobian matrices are obtained. The mathematical conditions that lead to singularities are also found. Moreover, a geometric description of the boundaries of the workspace is given, which can be expressed using simple equations. Finally, some design examples are proposed and a prototype is presented.

A novel 3-[R(RR-RRR)SR] kinematically redundant 6+3-degree-of-freedom (dof)spatial hybrid parallel robot with revolute actuators is proposed. The kinematic model is developed based on the constraint conditions of the robot. It is shown that the type II (parallel) singularities can be completely avoided, thereby greatly extending the orientational workspace. Mechanisms are then introduced to use the redundant degrees of freedom of the robot to operate a gripper with the robot actuators, which are mounted on or close to the base. A CAD model of the robot is shown and a computer animation is provided to demonstrate the resulting architecture, which has full 6-dof capabilities and a large orientational workspace.

This paper presents a novel robotic hand design that aims at producing a realistic human-robot handshake. A standard characteristic model of the human-palm compliance is developed based on human hand anatomy and an empirical study. Based on this model a realistic palm-compliance rendering is implemented. The backdrivability of the system allows a position-controlled feedback loop which renders human-like agility. An objective and a subjective experimental session, also depicted in the accompanying video, are then presented in order to validate the haptic feedback of the robotic hand in comparison to a real human handshake.

This paper introduces a novel family of singularity-free kinematically redundant planar parallel mechanisms that have unlimited rotational capabilities. The proposed mechanisms are akin to conventional three-degree-of-freedom planar parallel mechanisms. By introducing a novel kinematically redundant arrangement, four-degree-of-freedom parallel mechanisms are obtained that can completely alleviate singularities and provide unlimited rotational capabilities. The kinematics of the mechanisms are derived, and the Jacobian matrices are obtained. It is shown that the singularities of this type of mechanism are governed by the orientation of a passive link connecting the redundant leg to the platform and that the latter orientation is easily controlled using the kinematic redundancy, thereby alleviating all direct kinematic singularities. An example mechanism is proposed, and a prototype is demonstrated. Example trajectories that include full cycle rotations are shown. The prototype also illustrates the use of the kinematic redundancy for an auxiliary task, namely grasping.

Haptic devices have been used to help people to learn or recover specific movements. An interesting application is the handwriting. In this paper we present a haptic device designed to help people to improve their writing skills. Guided by a teacher, who controls one of the mechanisms providing the haptic feedback, a group of students were asked to write few words using their second hand. The test led to some interesting outcomes. A quantitative analysis is then carried out in order to support the considerations uniquely based on the qualitative observation of the results.

This paper presents the design and experimental validation of an anthropomorphic underactuated robotic hand with 15 degrees of freedom and a single actuator. First, the force transmission design of underactuated fingers is revisited. An optimal geometry of the tendon-driven fingers is then obtained. Then, underactuation between the fingers is addressed using differential mechanisms. Tendon routings are proposed and verified experimentally. Finally, a prototype of a 15-degree-of-freedom hand is built and tested. The results demonstrate the feasibility of a humanoid hand with many degrees of freedom and one single degree of actuation.

This paper presents a new type of haptic device using spherical geometry. The basic idea of haptic devices is to provide users with feedback information on the motion and/or force that he or she generates. Haptic devices have several potential applications such as, for example, fine compliant assembly, VR environment simulation, and high-precision teleoperation, especially in hazardous or hostile areas. The particular architecture of the spherical haptic device developed here will be presented and its advantages will be highlighted. Then, its basic kinematic properties, which shall be used for control and geometric optimization purposes, will be reviewed. The design optimization itself will then highlight some important features of the mechanism. The control scheme and real-time force feedback issues will then be presented. Finally, the results obtained with the prototype will be discussed.

This article presents a path planning strategy for redundant serial manipulators working in a cluttered environment. Developed in a practical context of telemanipulation, the algorithm, which sacrifices the capability of solving very difficult trajectories for efficiency, allows a human to control a robot at a higher level, in Cartesian space. The model of the environment is provided by a 3D vision system as an occupancy map. An iterative process guides the end effector towards its goal with the help of discrete potential fields, which reduce the number of local minima. The motion of the manipulator is calculated using the velocity inversion of a redundant manipulator, which optimizes the distance to obstacles. The algorithm includes joint limit constraints, collision detection and heuristics for the solution of typical difficult cases, thereby leading to a high success rate. A simulator has been developed to test the algorithms.>