Twists and wrenches, as defined in screw theory, are commonly used tools to establish the input/output velocity relationship of linkages, where the output velocity is written as the product of a Jacobian matrix and the input velocity array. However, for parallel mechanisms and, more generally, mechanisms with arbitrary topologies, this Jacobian matrix is typically derived through at least one numerical matrix inversion. This step may introduce numerical errors, particularly due to inconsistent units across the matrix components. This paper presents a new method for explicitly formulating the Jacobian matrix of a broad class of linkages. This class includes all planar and spherical linkages, but also parallel mechanisms whose end-effector may only translate or rotate about a fixed point, regardless of topological complexity. Central to this method is a new matrix called thetwist matrix, constructed from appropriately chosen wrenches. Using this matrix, the Jacobian of any body within the mechanism, not just the moving platform, can be derived explicitly as a combination of elementary twist matrices, independently from the mechanism's complexity.

This paper details the simulation and experimental validation of an autonomous perching and take-off method for a multirotor unmanned aerial vehicle (UAV) using a suction cup perching mechanism on vertical surfaces. The suction cup interaction with different surface types is characterized with experimental tests to accurately model the perching manoeuvre. The resulting model is used to develop a realistic hardware-in-the-loop (HIL) simulation of the perching and take-off manoeuvre of the UAV in Gazebo. A control method is developed to automate the perching and take-off manoeuvre. The method is tested in simulation and is experimentally validated with flight tests. Comparisons between simulation and experimental data demonstrate that the simulation is accurate and can be used to continue the development of autonomous perching methods.

This paper provides an overview of the latest trends in robotics research and development, with a particular focus on applications in manufacturing and industrial settings. We highlight recent advances in robot design, including cutting-edge collaborative robot mechanics and advanced safety features, as well as exciting developments in perception and human-swarm interaction. By examining recent contributions from Kinova, a leading robotics company, we illustrate the differences between industry and academia in their approaches to developing innovative robotic systems and technologies that enhance productivity and safety in the workplace. Ultimately, this paper demonstrates the tremendous potential of robotics to revolutionize manufacturing and industrial operations, and underscores the crucial role of companies like Kinova in driving this transformation forward.

Versatile and secure grasping in robotic systems remains a difficult challenge to address when objects possess a wide range of different properties (size, weight, friction coefficient, etc.). The human hand is often the primary source of inspiration for many technologies addressing this challenge, and a notable feature of our hands is that they can vary their stiffness to match the requirements of the task, e.g., become stiffer or more compliant depending on specific requirements. Many robotic devices have been proposed in the literature mirroring this capability, either using an adjustable internal tension mechanism similar to what happens with human tendons or another physical phenomenon yielding the same effect. This article proposes a new type of soft robotic fingers using a novel method to produce a variable stiffness achieved by modifying the kinematic structure of the fingers using snap-fit joints, a very simple alternative to most variable stiffness mechanisms. The resulting modification of the geometry and kinematics of the fingers, including their number of degrees of freedom, allows to greatly alter the intrinsic stiffness of the grasp produced by these fingers. A notable feature of the proposed new design is that one pair of fingers can be used to switch the stiffness of another pair if a dual arm robot is used.

This paper introduces a novel concept for a (self-)adaptive, a.k.a. underactuated, finger which presents the particularity of exploiting the traditional motion generated by standard robotic grippers for actuation. The kinematic structure of this finger allows for seizing objects of various shapes in both enveloping and precision grasps without having any actuator in its joints. Following a kinetostatic analysis, the forces generated by the finger will be obtained and analyzed. The performance of a practical implementation of the design will be subsequently evaluated and compared with another architecture inspired by a commercially available product. Finally, collision modes for safe human interaction will be presented and followed by the demonstration of a prototype.

Underactuated mechanisms are commonly used in robotic hands and grippers to improve their ability to adapt to the shape of an object. These underactuated mechanisms can be characterized by their global stiffness as measured by their actuator. Using this with self-adaptive fingers, it is possible to elaborate equations highlighting the relationship between the stiffness measurements and the contact locations. In this paper, a complete stiffness analysis of a general double tendon underactuated finger is performed with the aim of establishing the contact locations without any tactile sensors.

In this paper, it is proposed to use spatial differentials instead of independently actuated cables to drive cable robots. Spatial cable differentials are constituted of several cables attaching the moving platform to the base but all of these cables are pulled by the same actuator through a differential system. To this aim, cable differentials with both planar and spatial architectures are first described in this work and then, their resultant properties on the force distribution is presented. Next, a special cable differential is selected and used to design the architecture of two incompletely and fully restrained robots. Finally, by comparing the workspaces of these robots with their classically actuated counterparts, the advantage of using differentials on their wrench-closure and wrench-feasible workspaces is illustrated.

In this paper, the idea of using cable differentials in the architecture of planar cable-driven parallel robots is introduced. Cable differentials are a type of mechanisms with several outputs driven by a single input. Using them in cable parallel manipulators can decrease their cost and control complexity. However, due to their kinematic constrains, cable differentials cannot be arbitrarily used in the design of these manipulators. Thus, a synthesis method is proposed to tackle this issue. First, the general requirements and characteristics of differentially driven planar cable mechanisms are reviewed. Then, the advantages of using these differentials instead of typically actuated cables are shown through a comparison between differentially actuated planar cable robots and fully actuated ones. The results reveal that with the same number of actuators, using differentials may lead to larger workspaces and improved kinetostatic properties. Subsequently, the systematic synthesis of differentially driven planar cable mechanisms is presented. For this, a method to find the different arrangements of q cables in a differential is proposed. Then, valid arrangements with 2, 3, and 4 cables are investigated. Finally, several differential actuation schemes are considered and all possible differentials with q=2, 3, and 4 cables are found.

This paper proposes a control scheme dedicated to underactuated fingers with the intention of maximizing the capabilities of the latter using tactile and position information at a minimum cost. Tactile sensors are implemented on one prototype of underactuated finger and used to enhance the behaviour of the hand despite its limited number of control signals. First, tactile technology is briefly recalled and discussed. Second, the electronic design of the sensors' controller is presented. Third, a real-time control scheme is introduced, based on a fuzzy force control method. Finally, a slippage prevention technique is presented. Results are discussed based on experimental observations and indicate that the behaviour of underactuated fingers can be substantially enhanced with tactile information and a classic fuzzy control approach.

The aim of this paper is to establish a fundamental basis for the analysis of underactuated fingers with a general approach. A new method to obtain the force capabilities of any underactuated fingers will be presented. Force capability is defined as the ability to generate an external wrench onto a fixed object with a given set of phalanges. This method is based on the introduction of two new matrices which completely describe the relationship between the input torque of the finger actuator(s) and the contact forces on the phalanges. Using this tool, one can study the conditions under which certain phalanx forces vanish, and compare different underactuation mechanisms with a rigorous approach.

This paper studies the force capability of a particular class of underactuated fingers. Force capability is defined as the ability to create an external wrench onto a fixed object. The concept of the underactuation in robotic fingers, with fewer actuators than degrees of freedom (DOF) through the use of springs and the mechanical limits, allows the hand to adjust itself to an irregularly shaped object without complex control strategy and numerous sensors. However, in some configurations, the force distribution in an underactuated finger can degenerate. The finger can no longer apply forces on the object, leading in some cases to the ejection of the latter from the hand. This paper focuses on a 2-DOF finger and studies its ability to seize objects with a secure grasp.

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.