This report investigates two strategies for the design of extension springs suitable for various proportions of a two-degrees-of-freedom (dof), 2-RRS-1-RRRR cable-actuated mechanism. The design strategies seek feasible designs for extension springs conforming to geometrical constraints on free length and outer coil diameter, as well as strength-based constraints defined by factors of safety at critical locations in the coil and hooks.

Upper limb wearable exoskeletons are devices used for assistive and augmentative applications in work environments. The shoulder mechanism of the upper limb exoskeleton is vital in fulfilling its objective by exhibiting its capability to move with the human shoulder in unity without any joint axis misalignment. Any misalignment can cause strain on the human shoulder complex due to unwanted interaction forces between the user and the exoskeleton. Most existing portable assistive or augmentation exoskeletons fail to exhibit the capability to self-align when there is a joint axis misalignment due to design-related issues. This paper presents the design, analysis, and experimental evaluation of a novel human-centric shoulder exoskeleton with a self-aligning shoulder mechanism for an average adult male. The novelty of the design is that it considers the human shoulder’s humeral head (HH) translation and incorporates a novel mechanism to reduce misalignment. The system’s design details, workspace analysis, and prototype testing and analysis are explained. The proposed exoskeleton is evaluated and validated using simulation and experimentation on a standardised test bench. The results are compared with the existing conventional exoskeleton and human-assisted motion, and it was found that the proposed exoskeleton is capable of reducing the interaction forces due to misalignment by 99%. Further, a simple assistive control architecture is proposed and implemented for the exoskeleton for efficient operation.

Robotic manipulators synthesised using lower-mobility cable-actuated joints are interesting candidates that bridge the stiffness gap between soft and rigid counterparts. Their inherently higher stiffness over soft robots facilitates higher payload manipulation capabilities. At the same time, their lower but variable-stiffness capabilities and higher payload-to-mass ratios when compared with rigid industrial manipulators encourage deploying such classes of mechanisms for cobotic applications. In this work, an optimal design of a 3-cable-actuated, 2-degree-of-freedom spatial variable-stiffness mechanism is investigated. For kinematic modelling, the loop-closure constraint equations are solved using polynomial homotopy continuation, which yields multiple inverse-kinematic solutions for a given pair of independent task-space inputs. In static modelling, the wrench-feasible workspace (WFW), stiffness characteristics, and the design of extension springs mounted in parallel with the cables for stabilising the mechanism are discussed. A screw-theory-based static force model is also presented to determine the reaction wrenches developed at each joint, and its predictions are validated using the ADAMS multibody dynamics package. Finally, a Gaussian-process-assisted multiobjective optimisation framework is employed for the simultaneous maximisation of the WFW and stiffness parameters.

The DELTA manipulator is famous for its fast execution of tasks. This brings the ability of this robot to be used in scenarios of fast execution of tasks in an underwater environment. This capability is investigated by assigning a desired trajectory to both the underwater vehicle (UV) and the manipulator. Initially, the kinematics and dynamics of UV and DELTA are derived. Then, the forces exerted on the vehicle by the DELTA manipulator motion are considered as external interferences affecting the vehicle. Sliding mode control compensates for these external disturbances, and the vehicle follows the desired trajectory. Error in position of the UV and also the end effector is within 1 cm from the numerical analysis. The maximum actuator torques were less than 15 Nm.

Wheeled mobile robots in today’s world are the most common mobile robots. But most of these robots are smaller in size and lighter in weight. Generally these robots are programmed to velocity of 1 m/s, with kinematic control scheme. In the present work, a four wheeled mobile robot of 114.39 kg mass is modeled to move with a linear velocity of greater than 3 m/s. At this speed, due to the centrifugal force experienced by the robot, it is controlled by a model-based dynamic control scheme. The mathematical model of the robot is developed using MATLAB 2021b software and its CAD model is prepared using SolidWorks 2019 software. By simulation result it is found that the robot was stable at a constant acceleration of 0.2 m/s2 for a 10 s of simulation time and followed the desired helical trajectory successfully.

This work presents an inverse kinematics (IK) formulation of a spatial, cable actuated 2-degree-of-freedom mechanism. The 2-RRS-1-RRRR mechanism studied in this work is derived from the well-known quaternion joint. The system of 13 constraint equations have mixed variables in joint and task spaces, and is solved using polynomial homotopy continuation. Further on, the extraneous solutions are eliminated using the filtering conditions.

The human shoulder joint is a complex structure capable of bearing enormous loads and performing intricate movements in three-dimensional space. Consequently, it is imperative for existing exoskeletons to be compatible with and possess highly synchronous motion profiles that are similar to those of a human shoulder joint. Due to the movement of the humeral head within the glenohumeral joint, an exoskeleton mechanism aligning with the shoulder joint cannot be constructed as a mutually perpendicular actuated system. This misalignment could result in an axis mismatch between the human shoulder joint and the exoskeleton, potentially causing interaction forces and joint injuries. This review article explores the significance of the humeral head translation from the glenoid fossa of the scapula during humerus elevation in the human shoulder joint and its impact on the design of upper limb exoskeletons. The effect of various design elements on the stability of the glenohumeral joint in an upper limb wearable device is discussed, underscoring the need to correct this misalignment during the design phase. This paper also compares the work done by different authors regarding the experimental calculation of the range and directional pattern of humeral head translation based on the range of elevation. It further compares existing exoskeletons based on their range of motion, actuation, portability, mechanism, transmission, and control schema, all of which contribute to the glenohumeral stability of the user.

Unmanned surface vehicles (USVs) emerged as one of the important classes of marine vehicles, and have a wide range of applications ranging from transportation to ocean research. Model or system uncertainties and disturbances from the harsh marine environment make the operation of USVs on the water surface more challenging. The robust trajectory tracking problems of USVs are still an emerging control engineering research domain. Most of the works already conducted in the field only considered the efficacy of the control schemes without addressing the actuator characteristics like energy efficiency, chattering, and saturation. This study proposes a sliding mode control (SMC) in which disturbance estimation is enhanced by Gaussian process regression (GPR). The proposed control scheme reduces the tendency of overestimation with the help of GPR while ensuring the accuracy of trajectory tracking by SMC in the presence of model uncertainties and external perturbations. The stability of the proposed SMC-GPR control method has been confirmed using Lyapunov's theory.

Soft Robotics is an emerging field with the potential to address real-world problems with newer possibilities and safer human–robot interactions. Generally, soft robots comprise materials with moduli ranging from 104 to 109 Pa. The significant characteristics of soft robots include their high flexibility, compatibility, and superior environmental adaptability. Despite the several advantages of soft robots, many physical limitations exist due to their structural compliance and the viscoelastic behaviour of the material which leads to non-linear deformations in the material. This very reason necessitates sophisticated and novel sensing, actuation and non-linear control methods for soft robots. This review paper provides a comprehensive understanding of the advancements in soft robots and finally outlines the gaps in this field, currently limiting their usage in several applications. The pros and cons of the various technologies are discussed, and possible strategies for the superior performance of soft robots and their prospects are outlined in this paper.

Manipulability analysis of humanoid robots with redundant arms is difficult due to the presence of large number of Degrees of Freedom (DOF). Most researchers address manipulability issues without considering the effects of joint limits, obstacles and singular spaces in a Cartesian workspace. Hence, development of an accurate manipulability analysis technique, which can increase task performance by considering the above-mentioned issues is crucial for completing cooperative and non-cooperative tasks. Our paper proposes a new approach for determining manipulability measurements of a humanoid robot with redundant arms doing coordinated and non-coordinated tasks by analysing manipulability ellipsoids constructed through a desired trajectory. Penalty functions for compensating joint limits and avoiding obstacle regions are multiplied along with a Jacobian matrix to generate an Augmented Jacobian matrix. Manipulability ellipsoids determined using the Augmented Jacobian for individual configurations are compared with desired manipulability ellipsoids for finalizing the joint solutions. The advantages of proposed approach over conventional approach and significance of employing proposed approach for updating joint configurations are presented in this paper. The experimental validation of the proposed method using a developed humanoid robot is also given in this paper.

This paper presents the design and dynamic analysis of a reconfigurable four-wheeled mobile robot, with front wheels capable of transforming from a conventional circular wheel into a five-spoke wheel-legged (wheg) configuration. The transformation is achieved through a reconfiguration mechanism integrating a slider-crank chain with a rack and pinion system. A comprehensive dynamic analysis of the mechanism is conducted to evaluate the torque requirements for actuation and to support the selection of a suitable off-the-shelf motor. The required actuation torque is primarily influenced by the normal contact (reaction) force between the wheel and the ground or terrain, which varies depending on surface or terrain conditions. This contact force is computed using system dynamics, and its variations are further analyzed through the robot’s dynamic response. Numerical simulations, supported by real-world field tests, validate the effectiveness of the proposed design in moderately uneven environments.

Transradial amputation, or the loss of the arm below the elbow, significantly upsets a person’s ability to perform everyday tasks and can lead to profound psychological and emotional distress. Traditional prosthetic arms are heavy, expensive, and require constant maintenance which limits their broad use. This paper presents the design of a lightweight and inexpensive prosthetic arm for people with transradial amputations. Through the utilization of 3D printing technology and the incorporation of readily available materials and off-the-shelf components, a prosthetic arm was created that is both adaptable to the needs of the individual and suitable for use in low-resource environments. The design addresses the limitations of traditional prosthetic arms, by providing a more accessible alternative that can improve the quality of life for amputees. The proposed hand has three articulated fingers: the thumb, the index, and the middle finger with 3 DOF for each finger and 1 DOF for the thumb’s abduction and adduction. Overall, the proposed design of a lightweight and cost-effective prosthetic arm for individuals with transradial amputation offers a functional and affordable alternative to traditional prosthetics.

The human need for rehabilitation, assistance, and augmentation has led to the development and use of wearable exoskeletons. Upper limb exoskeletons under research and development are tested on human volunteers to gauge performance and usability. Direct testing can often cause straining of the joints, especially the shoulder joint, which is the most important and flexible joint in the upper extremity of the human body. The misalignment of joint axes between the exoskeleton and the human body causes straining. To avoid this, we propose designing and developing a novel human shoulder phantom mimicking the shoulder complex motion and the humeral head translation that can help in the real-time testing of exoskeletons without the need for human volunteers. The device can be used to test the interaction forces and the maximum reachable position of the exoskeleton. It consists of three degrees of freedom (DOF) passive shoulder girdle mechanism and seven DOF glenohumeral joint mechanisms, of which six are passive revolute joints and one is an active prismatic joint mimicking the humeral head translation. All the passive joints are spring-loaded and are incorporated with joint angle sensors. A custom-made, three-axis force sensor measures the human-exoskeleton interaction forces. The design details, selection of joint springs, linear actuation mechanism, and the analysis of the phantom's reachable workspace are presented. The device is validated by comparing the interaction forces produced during the conventional exoskeleton-assisted and human-assisted phantom arm elevation.

This paper presents a novel rotary actuator's design concept based on shape memory alloy (SMA) springs and permanent magnet systems. The proposed actuator is so designed that it can operate even in a vacuum. The presence of permanent magnets leads to efficient and quick rotation motion without any direct contact between the actuation system and passive disc rotation. The presence of a smart actuator (SMA) system helps build a lightweight actuator. The presented actuator converts the translational motion of the SMA springs in the bi-directional rotation of the passive disc. The contraction of the SMA could directly control the rate of rotation.

The conceptual design and simulation analysis of a four-wheel reconfigurable robotic plat form for Search and Rescue (SAR) operations in unstructured environments, has been presented in this research. Unlike other solutions that rely on fixed-radius or track-based systems, this design features an innovative wheel architecture that transitions between a conventional circular wheel and a five-spoke configuration. By selectively altering the geometry of the wheel, the robot can maximize maneuverability and ground clearance in real-time, thus enhancing its versatility across multiple terrains. System performance is verified through multibody simulations using MSC ADAMS. The results confirm that reconfigurable wheels can significantly expand the operational envelope of SAR robots without sacrificing design simplicity or energy efficiency.

Gripping devices for harvesting fruits have such types of work as cutting, tearing and unscrewing. For apples, it ispreferable to use slicing or unscrewing, while the fruit leg should not remain, damaging the apple during storage.In this article, we are developing a grab for harvesting apples. The gripper is used both for holding the fruit and forjamming, followed by unscrewing. One of the advantages is that the proposed method of collecting apples allowsyou not to waste time moving the manipulator from the tree to the basket, but only to grab and tear them off. Thefruit enters the gripper device; after which it enters the fruit collection container through a rigid or flexible pipe.The gripper device is built on the basis of a ball-screw transmission, which is supplemented by a gear drive alongthe helical surface. This allows for rotation and rectilinear movement of the held fruit. The gripping device has aratchet mechanism that allows you to fix the fruit. A mathematical model of the gripper device has been developed,which allows determining the torque of the engine depending on the position of the fingers. The parameters of themechanism were optimized using a genetic algorithm, and the results are presented in the form of a Pareto set. A3D model of the gripper device has been built and a layout has been developed using 3D printing. Experimentallaboratory and field tests of the gripping device were carried out.

This work focuses on the development of a lightweight exoskeleton designed specifically for the knee joint and integrating a virtual reality football environment. The primary goal is to enhance mobility and improve the quality of life for individuals with knee impairments, particularly those with weakened muscles and those recovering from knee surgery. This work introduces a Cable-Controlled exoskeleton technology for rehabilitation. It is lightweight, adaptable to patients who are recovering from knee surgery and having weak muscles, and engineered to facilitate targeted support during knee rehabilitation exercises in a sitting posture. This technology aims to enables biomechanical assistance, enabling patients to execute personalized, controlled movements that align with their rehabilitation needs. This work focuses on the design, modelling and analysis that is stress analysis, strain analysis, displacement analysis kinematic modelling, dynamic modelling of the system as well as the bowden cable, developing a control system and cubic trajectory of a knee exoskeleton for knee rehabilitation targeting patients. Drawing inspiration from existing research in rehabilitation robotics, this project aims to reduce bulkiness cost-effective and personalized solution for enhanced knee rehabilitation.