Rehabilitation robotics offers a promising approach to enhancing recovery in patients with musculoskeletal or cerebrovascular injuries. This article presents the development and validation of a novel variable stiffness joint (VSJ) that replaces large motors to generate resistive forces, thereby facilitating controlled recovery of muscle tone. For a revolute joint mechanism, we show that a constant output force can be maintained by adjusting stiffness, as demonstrated through simulation studies. Further validation was conducted through prototype experiments with volunteer participants, confirming that spring-length control enables modulation of joint stiffness and maintains a constant force at the link's end regardless of the rotation angle or trajectory. This work highlights an effective actuation method capable of delivering personalized and responsive rehabilitation therapy.

This paper presents a novel, compact four-degree-of-freedom (4DoF) integrated motion-tracking device (IMTD) designed for training and evaluation in laparoscopic surgery. The device's kinematics, mechanical design, instrumentation, and prototypes are developed and presented to meet the specific requirements of laparoscopic training context, including movement around a fixed center of motion and seamless integration into standard box trainers. The system IMTD's tracking accuracy and reliability are compared to a motion capture (MoCap) system, assessing its ability to capture both angular and translational motions of surgical instruments. The study then focuses on key performance parameters including precision, fluidity, speed, and overall motion efficiency. The results highlight the system's effectiveness in tracking surgical gestures, providing valuable insights into its potential as a tool for training and performance evaluation in minimally invasive surgery. Additionally, IMTD's low cost and integrated design allow for easy integration and implementation in training rooms, offering a practical and accessible solution for general use. By offering objective, real-time feedback, the system can significantly contribute to improving surgical skills and shortening the learning curve for novice students, while also providing a foundation for future development of gesture scoring algorithms and standardized training protocols.

This article deals with the development of a 6-degrees-of-freedom (DoF) hybrid interface for a teleoperated robotic platform intended to assist surgeons in cervical spine surgery. The targeted task is the drilling of cervical vertebrae for the attachment of spinal implants. Given the complex anatomy of the cervical region, with the proximity of the spinal cord and vertebral arteries, high accuracy in the drilling procedure is required to avoid complications for the patient. In this context, the proposed hybrid interface has been designed to meet the requirements of the drilling task, in terms of degrees of freedom, workspace, and force feedback, which have been identified through a literature review. It consists of an association of two parallel mechanisms and a centrally located serial mechanism. Direct and inverse kinematic modeling of each mechanism and one of the complete interfaces were carried out. A study of the dexterity distribution of the parallel mechanisms was carried out to select the suitable interface working mode that would keep the singularities away from the prescribed workspace. In addition, the force feedback was implemented in static mode, neglecting in the first time the weight of the system. The interface design parameters were then optimized to avoid singularities within the prescribed workspace, to minimize motor torques, and to reduce the size of the interface. These development stages led to the design of a motorized prototype of the hybrid interface.

This study aims to validate the performance of SurgTrack, a compact four-degree-of-freedom motion-tracking device specifically designed to guide and monitor laparoscopic surgical instruments in a training setup. The system’s kinematics, design, and instrumentation are presented in detail. To assess its accuracy, motion data collected from SurgTrack was analyzed and compared against a motion capture (MOCAP) system, evaluating its ability to track both angular and translational movements of surgical instruments. Additionally, a typical surgical training task was performed, and the system’s performance in tracking surgical gestures was analyzed. The results highlight SurgTrack’s ability in capturing surgical motions, demonstrating its potential as a valuable tool for training and performance evaluation in minimally invasive surgery. By providing objective feedback, the system can significantly contribute to improving the learning curve of surgery students.

This paper presents the validation of a teleoperation system designed for remote center of motion (RCM) tasks, such as laparoscopic surgery. Robotic-assisted surgical systems have significantly enhanced precision and patient outcomes, yet challenges remain in ensuring intuitive and adaptive control between the surgeon and the robotic instrument. To address these challenges, this work introduces a master-slave teleoperation framework that incorporates a non-homothetic control approach, allowing for asymmetric motion scaling and adaptive kinematic mapping between the master and slave devices. Unlike conventional homothetic systems, which rely on direct proportionality between input and output motions, the proposed method compensates for structural and functional differences in the master and slave robots. By combining parallel and serial kinematics in the master device, the system effectively manages constraints associated with fixed-center rotation mechanisms, commonly found in medical robotics. Experimental validation demonstrates that the system enhances dexterity, stability, and responsiveness, particularly in complex surgical maneuvers where precise motion adaptation is critical. The results confirm that the non-homothetic transformation significantly improves the surgeon’s ability to perform delicate operations, ensuring greater control of fidelity and ergonomic efficiency in robotic-assisted procedures.

This paper addresses the insufficiency of trained echography personnel in developed countries and the need for specialized skill development by introducing a novel 6-DOF parallel Cartesian haptic device for initial sonography training. The proposed mechanism consists of two identical limbs linked by a tool rod with a high-pitched screw for precise vertical actuation. Equipped with a functional sonography probe and a self-rotation mechanism using constant velocity joints, the system enables scanning of body phantoms to simulate pathologies. The direct and inverse kinematics are analyzed to determine the probe’s position and orientation. The developed concept is designed to provide force feedback with values closer to those encountered in real scans while utilizing a structure built from affordable components. These advantages make it particularly appealing compared to existing systems, especially in developing regions.

The shortage of specialized sonography professionals and the need for efficient training methods have led to the development of various sonography training solutions. This paper introduces a cost-effective sonography training system, combining a parallel master haptic device, body phantoms for simulating pathologies, and specialized software. The proposed mechanism is a 5-degree-of-freedom (5-DOF) parallel robot with two identical parts fixed on a stationary frame. It features a probe for scanning body phantoms and a self-rotation mechanism. The direct and inverse kinematic problems are analyzed to determine the probe's position and orientation. The proposed system offers a more affordable alternative to existing sonography training solutions, which can be prohibitively expensive, especially in developing countries. It provides a more realistic scan representation, offering a potential solution to address the shortage of sonography specialists while delivering high-quality training.

The main objective of this paper is to discuss the experimental validation of a tele-operation system for remote center-of-motion tasks, such as laparoscopic surgery. This validation is based on the use of an extra sensor placed on the master manipulator. The tele-operation system is composed of a new hybrid haptic device (nHH) intended to be used as a master manipulator controlling a collaborative robot, used as a slave surgical robot. The resolution of the forward kinematic model (FKM) of the master device is performed experimentally thanks to the use of an extra sensor. The IMU, as the extra sensor, is installed on the serial part of the nHH device to measure the orientation and is enabled to solve the FKM of the parallel part of the nHH device. The use of an extra sensor reduces the calculation time, improves the accuracy of the KFM, and makes it suitable for real-time applications. The preliminary validation of the force feedback in the nHH workspace is validated. Experiments were conducted on the master–slave platform to validate the proposed approach. The results are promising, which proves that the nHH device presents a suitable performance for the desired task.

In this study, we focus on a 3DOF (RRR) spherical parallel manipulator (SPM) employed as haptic interface (HI) for teleoperation application. We started by presenting the kinematic model of the interface, its different working modes and identifying singularity zones within the operational workspace (WS). As a solution, a redundant architecture is proposed where we used a fourth motor to enhance the dexterity of the device. Subsequently, our study takes a closer look at the comparative analysis of working modes in the purpose of selecting the optimal starting configuration for our interface. This selection ensures an optimized torque distribution across various WS configurations where we respect the limit of torques for every motor in order to stay in a safe zone of control.

The variable stiffness joints (VSJ) provide nonlinear stiffness behavior. The VSJ can be used in articulated systems to improve the safety of human-robot interaction. A new VSJ is proposed in this paper based on the principle of antagonistic springs. The stiffness behavior is tuned when the lengths of the springs are adjusted. A motor is used to control the movement of a set of racks and gears. This latter set changes the springs’ lengths and thus the joint stiffness. Based on the mathematical model and in the case of the revolute joint, it is demonstrated that it’s possible to obtain a constant force due to the stiffness. The joint is attached to a link; the simulation results show that the joint provides the desired force at the end of the link. Physical experiments on the prototype were performed to verify the validity of the analysis results. The experimental results show that the control of the springs’ length allows, to vary the stiffness and therefore maintains a constant force at the end of the link regardless of the angle joint rotation.

In human-robot interaction environments, flexible mechanisms have been implemented to relate force and movement ensuring safe interaction. Variable stiffness joints add flexibility to a rigid mechanism and allow the position and the joint stiffness to be changed simultaneously. This paper presents a variable stiffness joint with an antagonistic configuration, with two springs as flexible elements, integrated into a device for arm rehabilitation assistance based on a five-bar mechanism. Joint provides to the device constant or variable torque at the end-effector by varying the length of the springs using an actuator attached to a set of gears and racks. The motor controls the gear position, which changes the size of both springs to modify the stiffness. Here, we give details of the joint mathematical model and the five-bar mechanism and present the simulation validation. A prototype was manufactured and integrated into the device to perform tests with volunteers who followed a desired trajectory. The data obtained are the joint's torque and the end-effector's constant force.

In this paper, we present the dynamic modelling of a geometrically non-uniform beam to predict anguilliform undulation of a bio-inspired flexible snake robot. The snake robot is proposed as a scientific tool and designed to fluidly mimic various anguilliform gait pattern. The snake skeleton consists of a series of compliant vertebrae with a variable stiffness along the body. An approach based on the finite element method coupled with an optimization problem, and solved using genetic algorithms method is presented to predict the snake robot skeleton undulation. The snake robot was approximated with an equivalent cylindrical beam made of a series of elements (vertebrae). The internal damping and stiffness were identified as a result of the optimization problem to retrieve similar ripple cone. Comparison between experimental robot undulation, and simulations is performed. It was demonstrated that the model is adapted to predict the real undulation of the a dead snake and as well as approximate the one of the snake robot undulation.

This paper focuses on developing a novel hybrid-haptic (nHH) device with a remote center of rotation with 4 DOFs (degrees of freedom) intendant to be used as a haptic device. The new architecture is composed of two chains handling each one a part of the motions. It has the advantages of a parallel robot as high stiffness and accuracy, and the large workspace of the serial robots. The optimal synthesis of the nHH was performed using real-coded genetic algorithms. The optimization criteria and constraints were established and successively formulated and solved using a mono-objective function. A validation and comparison study were performed between the spherical parallel manipulator and the nHH. The obtained results are promising since the nHH is compared to other similar task devices, such as spherical parallel manipulator, and presents a suitable kinematic performance with a task workspace free singularity inside.

Growing demands for improved surgical-related curricula have led to new training approaches. The ability to acquire surgical skills requires consistent practice. Many suggestions show that technical skills can be learned outside the operating room. Surgical simulation is one of the most widely practiced methods of learning in laparoscopic surgery in recent years. It offers medical students the opportunity to practice their surgical technical skills before passing them on the patient and entering the operating theater. Simulation learning, through training platforms, allows for detailed feedback and provides an objective assessment of acquired performance. Thus, the goal of training platforms is to best reproduce ecological (real) conditions and to offer the user a replica of the real situation as faithfully as possible. This paper is to propose a new concept of a platform for training and evaluation in laparoscopic surgery that approximates at best the real surgeons’ conditions practice.

This paper deals with the experimental validation of a novel hybrid haptic device (nHH) intended to be used in a robotic teleoperation platform for laparoscopic surgery. The contribution of this work is to cope with the complexity of the Forward Kinematic Model (FKM) of the nHH and to validate its resolution experimentally through the use of an additional sensor: an IMU attached to its end-effector (serial part). Thus, this sensor allows to measure the orientation of the end-effector, allowing to solve the forward model of the parallel part of the nHH. Experiments have been conducted on the prototype of the hybrid device and, as expected, the FKM computation time is reduced. The proposed approach is validated and the obtained results demonstrate the significance of placing an IMU sensor on the serial part of the device, which makes the nHH suitable for real-time applications.

In robotics, the variable stiffness joints have been developed as an alternative to include flexibility to a rigid mechanism. Variable Stiffness Joint (VSJ) allows for varying the stiffness in a mechanism during the performance of a trajectory. The development of this joint has increased, and various applications have emerged, most to improve human-robot interaction. This paper presents a VSJ based on the principle of antagonistic springs with a set of gears and racks that allow the extension or compression of the springs. The joint provides constant torque or variable torque to obtain a constant or variable force at the output of the link, so a relationship is between the torque provided by the spring’s effort and the output force; however, it is possible to achieve a desired variable force with this joint design. Simulations are realized to obtain the behavior for both a constant and a variable force.

This paper presents an approach to improve the resolution of the forward kinematic model (FKM) of parallel manipulators. This approach is based on placing sensors on one leg of the manipulator rather than placing them on the actuated joints at the base. Using this method, we aim to cope with the complexity of the FKM of parallel manipulators and to improve the computation time of the FKM. The proposed method is applied on two different robots, i.e.: the 3-UPU and RAF manipulators which are Translational Parallel Manipulators (TPMs). Simulations were carried out to validate this method. These simulations show how the serial approach improve the accuracy, overcome singular configurations inside the workspace and speed up the resolution of the FKM.

Bioinspired robots are useful tools to study complex biomechanical processes of animal locomotion. Key movements and kinematic parameters are under the control of experimenters, which is impossible to perform when experimenting with living animals. The primary challenge to test biological hypotheses is designing realistic robots taking inspiration from swimming snakes. Yet, underlying biomechanics of undulatory swimming i.e., anguilliform swimming, remains poorly understood. Many of underwater snakebots are made of rigid segments that form a broken-line system, unlike the skeleto-muscular systems of living snakes include more than 200 vertebrae, conferring an extreme fluidity. This paper introduces a novel design based on hybrid continuum cable driven robot (HCDR) developed through interaction with biologists and roboticists. This Biology-Push design significantly increases the fluidity and freedom of the robot's motion. Thus, improved mimic snake's locomotion is given using cable-driven to represent linkages between muscles and vertebrae providing good fluidity. In addition, the association of rigid and flexible parts allows a homogeneous distribution of actuators and masses to design autonomous swimming snake robot. Combining literature data and kinematic of swimming snakes’ analyses, we implemented a kinematic model to control prototype’ motion in both a plane and a volume. Finally, a comparative study between the device kinematics and the snake's movements is carried out.

Replicating animal movements with robots provides powerful research tools because key parameters can be manipulated at will. Facing the lack of standard methods and the high complexity of biological systems, an incremental bioinspired approach is required. We followed this method to design a snake robot capable of reproducing the natural swimming gait of snakes, i.e., the lateral undulations of the whole body. Our goal was to shift away from the classical broken line design of poly-articulated snake robots to mimic the far more complex fluid movements of snakes. First, we examined the musculoskeletal systems of different snake species to extract key information, such as the flexibility or stiffness of the body. Second, we gathered the swimming kinematics of living snakes. Third, we developed a toolbox to implement the data that are relevant to technical solutions. We eventually built a prototype of an artificial body (not yet fitted with motors) that successfully reproduced the natural fluid lateral undulations of snakes when they swim. This basis is an essential step for designing realistic autonomous snake robots.

Designing and modelling bioinspired robots enables mimicking complex biomechanical process as snake swimming locomotion. Cable-driven compliant continuum robot made of separated modules was specifically designed as biology-push process to accurately reproduce snake’s locomotion. This paper aims to present the design and modelling of a bioinspired two sections Serial Continuum Robot (SCR). This latter is a hybrid snake-arm composed of two sections assembled in series as a serial standard manipulator. Each section of the snake-arm is independently actuated and consists of 2-DoF. This polyvalent design combines the advantage of flexible continuum robot and serial manipulator. Swimming snake-like robot is presented as an example of biomimetic application, where the robot is able to significantly mimic snake locomotion with a homogeneous distribution of actuators.