Grasping has been a long-standing challenge in facilitating the final interface between a robot and the environment. As environments and tasks become complicated, the need to embed higher intelligence to infer from the surroundings and act on them has become necessary. Although most methods utilize techniques to estimate grasp pose by treating the problem via pure sampling-based approaches in the six-degree-of-freedom space or as a learning problem, they usually fail in real-life settings owing to poor generalization across domains. In addition, the time taken to generate the grasp plan and the lack of repeatability, owing to sampling inefficiency and the probabilistic nature of existing grasp planning approaches, severely limits their application in real-world tasks. This paper presents a lightweight analytical approach towards robotic grasp planning, particularly antipodal grasps, with little to no sampling in the six-degree-of-freedom space. The proposed grasp planning algorithm is formulated as an optimization problem towards estimating grasp points on the object surface instead of directly estimating the endeffector pose. To this extent, a soft-region-growing algorithm is presented for effective plane segmentation, even in the case of curved surfaces. An optimization-based quality metric is then used for the evaluation of grasp points to ensure indirect force closure. The proposed grasp framework is compared with the existing state-of-the-art grasp planning approach, Grasp pose detection (GPD), as a baseline over multiple simulated objects. The effectiveness of the proposed approach in comparison to GPD is also evaluated in a real-world setting using image and point-cloud data, with the planned grasps being executed using a ROBOTIQ gripper and UR5 manipulator. The proposed approach shows better performance in terms of higher probability for force closure with complete repeatability.

Human upper limb activities have been extensively researched in the field of biomechanics, rehabilitation, motion tracking, and augmented reality. Tracking joint angles to evaluate flexibility and overall range of motion is a widely accepted technique for human motion analysis. Traditionally joint angle evaluation is performed with the help of inertial measurement units including gyroscope, accelerometers, and other sensor modalities. However, it has some inherent limitations such as the increase in sensor drift and change in the rate of error because these sensors are susceptible to inaccuracies due to gravity and electrical interferences from the surroundings. The other alternatives are magnetic, ultrasound and marker-based visual sensors which are accurate but expensive, limiting their usage only to clinical settings. Hence the fusion of a low-cost vision-based sensor using computer vision with an inertial measurement unit is proposed in this paper to perform real-time joint angle estimation. This paper presents a robust, low-cost, and portable platform using inertial and vision sensors for real-time joint angle tracking for rehabilitative tasks. The proposed platform consists of two IMUs mounted over the upper arm and the forearm. The marker-less vision-based sensor using the mediapipe framework, tracks landmark key points. The observed RMSE for IMU-based estimation is 6.30 degrees and the vision-based sensor is 7.70 degrees. The efficacy of the proposed methodology was evaluated by simple rehabilitative exercises performed on healthy participants. Statistical analysis of the experimental results demonstrates that fused sensor output has reduced the RMSE by 6.18 degrees and has a close correlation with the ground truth values.

Among primates, the prehensile nature of the hand is vital for greater adaptability and a secure grip over the substrate/branches, particularly for arm-swinging motion or brachiation. Though various brachiation mechanisms that are mechanically equivalent to underactuated pendulum models are reported in the literature, not much attention has been given to the hand design that facilitates both locomotion and within-hand manipulation. In this paper, we propose a new robotic gripper design, equipped with shape conformable active gripping surfaces that can act as an active or passive joint and adapt to substrates with different shapes and sizes. A floating base serial chain, named GraspMaM, equipped with two such grippers, increases the versatility by performing a range of locomotion and manipulation modes without using dedicated systems. The unique gripper design allows the robot to estimate the passive joint state while arm-swinging and exhibits a dual relationship between manipulation and locomotion. We report the design details of the multimodal gripper and how it can be adapted for the brachiation motion assuming it as an articulated suspended pendulum model. Further, the system parameters of the physical prototype are estimated, and experimental results for the brachiation mode are discussed to validate and show the effectiveness of the proposed design.

Differentiating muscle fatigue induced hand tremor of surgeons into different discernible levels is important in laparoscopic surgery. Systematic clustering can be used as a method to assess the risk of hand tremor which can largely affect the surgical performance. The prime challenges lying here are the detection of fatigue onset and classification of fatigue induced tremor level in dynamic laparoscopic tool manipulation. Conventionally, muscle fatigue is assessed with frequency domain analysis of the surface electromyography (sEMG) signal, where the detection process is predominantly valid only for isometric contraction of muscles. Conventional methods cannot be used for assessment of fatigue level in case of dynamic activities as the task itself modulates the frequency content of the myoelectric response. In this paper, we have proposed a novel polynomial Hammerstein model-based clustering of fatigue induced tremor, employing sEMG, and joint torques. The sEMG signal, containing muscle fatigue information, gets fused in this model dynamically through a Kalman filter. Model parameter-based clustering of the fatigue induced tremor level was implemented on eight subjects. Optimal number of cluster centers were found to be appropriately coherent with the fatigue inducing task epochs of the experiment. In spite of the subjective variations, the model parameter-based clustering method was able to differentiate among the fatigue-inducing tasks for all the subjects. We have concluded that this model-based clustering can successfully differentiate between different levels of the fatigue induced tremor in dynamic activity of laparoscopic tool manipulation.

The design of a novel, soft bidirectional actuator which can improve the human-robot interactions in collaborative applications is proposed in this paper. This actuator is advantageous over the existing designs due to the additional degree of freedom for the same number of pressure inputs as found in the conventional designs. This improves the workspace of the bidirectional actuator significantly and is able to achieve higher angles of bidirectional bending at much lower values of input pressure. This is achieved by eliminating the passive impedance offered by one side of the bending chamber in compression when the other side of the chamber is inflated. A simple kinematic model of the actuator is presented and theoretical and finite element analysis is carried out to predict the fundamental behavior of the actuator. The results are validated through experiments using a fabricated model of the soft bidirectional bending actuator.

In this paper, we present the design of a novel, hybrid multipurpose robotic platform equipped with a pair of graspers to synergize grasping, manipulation, and locomotion. The multipurpose grasper consists of two underactuated fingers with an active gripping surface, which passively conforms to an object while grasping. Each finger has a spring loaded synchronous belt drive which functions as the active gripping surface. The grasper is capable of handling a range of objects with irregular geometry and size. Two such underactuated graspers are connected through a serial kinematic chain and this provides the platform both manipulation and locomotion capability. Graspers act as “legs” or “wheels” of the robot during locomotion and can easily adapt to terrain variations. Fewer number of actuators, simple and scalable kinematic structure, and computationally efficient control are some of the main features of the design. Design details and kinematic analysis are presented. Experiments were conducted on a prototype robot to demonstrate multiple modes of operation.

Underwater gliders are special class of autonomous underwater vehicles (AUVs) proven to be power efficient with better range and endurance compared to the conventional underwater robots. Most of the existing underwater gliders use `change of mass' based variable buoyancy (VB) method in which the overall system architecture and construction are complex. A novel underwater glider RoBuoy based on the `change of volume' concept of variable buoyancy method is presented here. RoBuoy uses actuated metallic bellows to change the volume which makes the system simple and modular in construction without any compromise in the performance. It uses minimal number of parts compared to the existing gliders which reduces the overall complexity of the system. Also, most of the conventional gliders use the external fluid for its working which may result in corrosion or fouling of parts and requires frequent maintenance. In the proposed glider, all the vital parts required for its working, apart from the sensing payloads are enclosed inside the hull, thereby increasing the durability. In this paper, a detailed design of RoBuoy is discussed with its possible modes of operation. An integrated mathematical model considering the individual dynamics of the actuator, hull/fuselage, and the wings has been developed and the open loop performance of the glider is studied at different input conditions. An experimental prototype has been designed and fabricated based on optimized dimensions, with the required mechatronic system. Experiments have been conducted and the results prove the feasibility of the concept.

This paper presents the design of a single use disposable compliant surgical tooltip for a tele-operated surgical robot. The proposed design aims at mitigating bio-fouling of surgical tools. By implementing a monolithic design for surgical tooltip, the cleaning and sterilization processes needed after every surgery for traditional surgical robotic tools is considerably simplified. The proposed design has 3 degrees of freedom (DOF) with a modified serpentine joint for enhanced buckling strength and off-axis stiffness. A magnetic force based coupling is proposed as a means of transferring power through a hermetic barrier to maneuver the tooltip. The tooltip is thus coupled through a hermetically sealed tool shaft preventing biological material from entering the tool shaft. By having a pluggable tooltip, modularity is also achieved by interchangeable tooltip instead of replacing the whole tool during surgery. A prototype of the proposed design is developed and its functional performance is validated. Owing to the magnetic nexus which forms the magnetic coupling, the tool is named MagNex.

Automated grasp planning for robotic hands is a complex problem when compared with the ease with which human hands grasp objects. Research in robotic grasp synthesis attempts to find novel ways in which a stable grasp can be achieved reliably. In this work, we present a grasping methodology that achieves optimized force closure grasps on 3D irregular objects. 3D objects in the form of polygonal meshes are parameterized to 2D shapes in order to reduce the search space by constraining robotic hands finger tips to be in contact with the objects surface. We use a Particle Swarm Optimization (PSO) based framework to optimize an initial grasp. The scheme has been validated on test-case 3D objects represented with surface tessellation for a 5-fingered DLR robotic hand.

Variable Buoyancy systems for selective deployment has been designed and the analysis of dynamics is discussed in this paper. Multiple interconnected VB modules have specific advantages in positioning the payloads like sensors and communication equipment at various depths to collect strategically important subsea data. The design of metallic bellow based Variable Buoyancy Systems (VBS) is presented along with the dynamic analysis of the module. The dimensions of the VB module are optimised to give best performance at the desired depth of operation. Effect of anchoring the module to a base station and cascading multiple modules for deploying at various depths have been studied in detail. Simulation results show that the cascaded VB modules can be successfully deployed for selective applications under various operating conditions.

Multiple robot systems are employed in various applications to get the complex tasks carried out by a group of robots. When Autonomous Underwater Vehicles (AUVs) are employed for underwater missions, they provide higher quality data, more coverage and reduces the mission time, thus resulting in huge cost savings. However, the formation control of such robots depends to a great extent on the communication requirements between the robots. In this paper, we propose a modified next-state approximation algorithm to control the leader follower formation of multiple AUV's which reduces the communication requirements. The controller drives each follower robot to the next desired position by eliminating the error between the next actual position of follower AUV, computed by considering its current and previous position and its next desired position by using a PID controller. Since this algorithm is independent of time step between states, the amount of information to be transmitted can be reduced by increasing the time steps. The design of the formation controller and its simulation studies for a group of AUVs are presented. The results confirm that the time step increase doesn't affect the path accuracy and hence the communication requirements get reduced.

This paper presents the design and analysis of a quadrotor with a novel configuration, VOOPS-Vertically Offset Overlapped Propulsion System. The objective of this configuration is to increase the payload capacity of a quadrotor without increasing the overall dimension and without compromising endurance. This has been achieved by vertically offsetting the propellers and allowing propeller overlaps so that an increase in propeller size can be achieved without any increase in the overall dimensions. The design details and the dynamic model of the VOOPS configuration are presented. The constraints on the design parameters such as propeller offset and overlap are determined using propeller deflection model and geometry respectively. The effects on change in the design parameters of VOOPS configuration were studied using bench tests and performance simulation of quadrotor with VOOPS configuration were carried out. Practical implementation of VOOPS configuration is also discussed.

Modern developments in the fields of control, sensing, and communication have made increasingly complex and dedicated underwater robot systems a reality. Used in a highly hazardous and unknown environment, the autonomy and dynamics of the robots is the key to mission success. Though the dynamics of underwater vehicle system is highly coupled and non linear in nature, decoupled control system strategy is widely used for practical applications. As autonomous underwater vehicles need intelligent control systems, it is necessary to develop control systems that really take into account the coupled and non-linear characteristics of the system. In this paper, we propose a control system with a nonlinear control strategy that takes into account the above factors. So far, AUV dynamics has often been derived under various assumptions on the motion of the vehicle. However, such assumptions may induce large modelling errors and may cause severe control problems in many practical applications. We propose to use both Lyapunov and state space back stepping based non linear control to overcome the modelling errors. The strategy will be tested through simulations for a flat-fish type AUV. Basic controller design and the simulation results will be discussed in the paper. A comparison of the results for conventional method and the proposed method will also be presented.