Ashitava Ghosal

• Ph D
• Professor (Full) at Indian Institute of Science Bangalore

This article presents three newer areas where robots are being used. The choice of areas is purely that of the author as there are numerous other areas where robots are being increasingly used. The article is an overview and attempts to present the science and technology behind these newer robotic applications.

Uniform thickness belleville springs(UBS) are a suitable replacement for coil springs in many applications due to their ability to take higher loads and their relatively small and compact size. This paper presents an experimental, numerical and theoretical analysis of the taper belleville spring(TBS). Experimental results on a normal taper bellevil...

This paper deals with generally routed, pre-bent cable-driven continuum robots (CCR). A CCR consists of a flexible backbone to which multiple disks are attached. Cables are passed through holes in the disk, and when pulled, the flexible backbone and the CCR can attain different shapes based on their routing and backbone configuration. An optimizati...

Cable-driven continuum robots (CCR) with generally routed cables are capable of achieving complex shapes, which a straight-routed CCR with multiple sections cannot achieve. This paper presents an optimization-based algorithm that can predict a routing and the amount of cable actuation required to attain a prescribed desired final shape in a CCR. Th...

A flexure-based three-degree of freedom (two rotations and one translation) is studied in this paper for application in an antenna pointing mechanism (APM). The antenna is rigidly connected to the moving platform of the manipulator. The platform is supported by three symmetrically arranged legs, and each leg has a revolute(R)-prismatic(P)-spherical...

Goal-directed eye, hand, and finger movements follow invariant kinematics consisting of approximate straight-line trajectories and bell-shaped velocity profiles. A fundamental unresolved issue is whether these trajectories are planned or whether they are a consequence of trajectory-free online control. We address this question using Spearmans rank...

An ideal dynamically isotropic Gough Stewart platform (GSP) has its first six modes of vibration as same, and this enables one to use effectively designed identical dampers to attenuate vibration from a source to a sensitive payload. A modified GSP (MGSP) capable of being dynamically isotropic is considered in this work. For a dynamically isotropic...

This paper presents as a study of a single leg of a quadruped robot with a compliance mechanism in its foot. The objective is to optimize the hopping behavior in terms of maximum jump height, least impact force for a minimum jump height, and power consumed in the actuators of the leg as a function of the compliance in the foot. The paper consists o...

A six degrees-of-freedom (DOF) two-radii Gough–Stewart Platform (GSP) can be designed to be dynamically isotropic and has been proposed for micro-vibration isolation. In many applications, the torsional mode can be ignored, and a 5DOF dynamically isotropic, parallel manipulator capable of attenuating three translational (3T) and two rotational (2R)...

A six degree of freedom (DOF) two-radii Gough-Stewart Platform (GSP) can be designed to be dynamically isotropic and has been proposed for micro-vibration isolation. In many applications, the torsional mode can be ignored, and a 5-DOF dynamically isotropic, parallel manipulator capable of attenuating three translational (3T) and two rotational (2R)...

In this paper, we consider a modified Gough-Stewart platform (MGSP) where two groups of three legs meet at two concentric circles on both top and bottom platforms. The geometry of the MGSP is chosen such that all the first six natural frequencies are equal for a typical payload mounted on the top platform. Additionally, in the top platform, made up...

A dynamically isotropic mechanism is useful for vibration isolation since such a mechanism can be used to attenuate the first six modes of vibration effectively and equally from a sensitive payload. A Gough-Stewart Platform (GSP) has been proposed, in literature, for six component vibration isolation. The conventional GSP, however, fails to give a...

Accurate modelling of continuum robots is required for predicting its motion and for model based control. In this work, we restrict our study to cable actuated continuum robots with a flexible backbone on which perforated disks are fixed and through which a cable is routed from the base to the tip. We compare two well known models, namely the optim...

Accurate prediction of shape and contact forces significantly improves the performance of a continuum robot during its operation in obstacle-laden environments. This paper presents an optimization-based mathematical framework to predict the bending profile of a cable-driven continuum robot in presence of obstacles. The kinematics model is derived f...

A human arm, up to the wrist, is often modelled as a redundant 7 degree-of-freedom serial robot. Despite its inherent nonlinearity, we can perform point-to-point reaching tasks reasonably fast and with reasonable accuracy in the presence of external disturbances and noise. In this work, we take a closer look at the task space error during point-to-...

Sharma, ShivamGhosal, AshitavaIn over-constrained mechanisms, all the joint reactions cannot be solved uniquely based solely on rigid body assumptions. However, a few joint reactions may be uniquely solvable, and an approach termed as reactions solvability analysis (RSA), in this paper, can be used to find such uniquely solvable joint reactions. Ex...

An estimated 50,000 people in India need a heart transplant annually. Today, one of the biggest challenges is practical: moving organs from one hospital to another. LifeBox is a device that addresses this problem with a system that extends preservation time of the heart, specifically to allow for increased travel time and distances. It utilizes non...

An elephant trunk robot is continuum robot consisting of a flexible backbone actuated by two pairs of cables (or tendons) offset by a distance and along the circumference of the backbone. By pulling the cables, the continuum robot assumes the shape of an arc of a circle in 3D space. In literature, forward kinematics of the robot has been developed...

Honeycomb sandwich laminates with aluminum and carbon fiber reinforce polymer (CFRP) face—sheets are widely used in spacecraft structures and aerospace industries. The damping behavior of such structures is reported to improve when the granular particles, called damping particles, are inserted in the honeycomb cells. The discrete element method (DE...

In this paper, with a view toward fast deployment of locomotion gaits in low-cost hardware, we use a linear policy for realizing end-foot trajectories in the quadruped robot, Stoch $2$. In particular, the parameters of the end-foot trajectories are shaped via a linear feedback policy that takes the torso orientation and the terrain slope as inputs....

With the research into development of quadruped robots picking up pace, learning based techniques are being explored for developing locomotion controllers for such robots. A key problem is to generate leg trajectories for continuously varying target linear and angular velocities, in a stable manner. In this paper, we propose a two pronged approach...

Continuum robots are becoming increasingly popular for applications which require the robots to deform and change shape, while also being compliant. A cable-driven continuum robot is one of the most commonly used type. Typical cable driven continuum robots consist of a flexible backbone with spacer disks attached to the backbone and cables passing...

In this paper, with a view toward fast deployment of learned locomotion gaits in low-cost hardware, we generate a library of walking trajectories, namely, forward trot, backward trot, side-step, and turn in our custom-built quadruped robot, Stoch 2, using reinforcement learning. There are existing approaches that determine optimal policies for each...

Stewart-Gough platform (SGP), a six-degree-of-freedom device that has been used extensively for isolating sensitive payload from micro-vibrations in spacecraft. In this paper, we propose a design where the first six modal frequencies are close to each other, for a predefined payload, thus enabling development of effective vibration isolation for al...

This paper deals with the design, development, modeling and experimental validation of a prototype endoscopic attachment that can be actuated independently by soft actuators to position an endoscopic catheter tip to a desired location. The soft actuators are miniaturized pneumatic artificial muscles (MPAMs) and by applying 137 kPa–827 kPa pressure...

It is commonly thought that visuomotor adaptation is mediated by the cerebellum while reinforcement learning is mediated by the basal ganglia. In contrast to this strict dichotomy, we demonstrate a role for the basal ganglia in visuomotor adaptation (error‐based motor learning) in patients with Parkinson's disease (PD) by comparing the degree of mo...

Cable-driven continuum robots find applications in bio-inspired robotics and medical robotics. Kinematics of cable-driven continuum robots, also called elephant-trunk robots, with straight cable routing is well studied in the literature. However, there are very few studies on the kinematics of continuum robots with general cable routing, despite it...

In this work, we provide a simulation framework to perform systematic studies on the effects of spinal joint compliance and actuation on bounding performance of a 16-DOF quadruped spined robot Stoch 2. Fast quadrupedal locomotion with active spine is an extremely hard problem, and involves a complex coordination between the various degrees of freed...

In this paper, we present the design, development, modelling and experimental validation of an endoscopic attachment that can be used to independently position an endoscopic catheter tip to a desired location. Three Miniaturized Pneumatic Artificial Muscles (MPAMs) are used in a flexible endoscopic attachment, each MPAM is of 1.2 mm diameter and 45...

It is commonly thought that visuomotor adaptation is mediated by the cerebellum while reinforcement learning is mediated by the basal ganglia. In contrast to this strict dichotomy, we demonstrate a role for the basal ganglia in visuomotor adaptation (error-based motor learning) in patients with Parkinsons disease (PD) by comparing the degree of mot...

Equipment panels of a spacecraft are made up of a sandwich composite with aluminum face sheets and a honeycomb (HC) core. The HC sandwich plate responds to the launch vibration loads subjecting the equipment mounted on it to a high level of accelerations at resonances owing to a lower natural damping. Damping particles (DPs) when inserted in the em...

In this paper, we present a complete description of the hardware design and control architecture of our custom built quadruped robot, called the Stoch. Our goal is to realize a robust, modular, and a reliable quadrupedal platform, using which various locomotion behaviors are explored. This platform enables us to explore different research problems...

Humans and animals are believed to use a very minimal set of trajectories to perform a wide variety of tasks including walking. Our main objective in this paper is two fold 1) Obtain an effective tool to realize these basic motion patterns for quadrupedal walking, called the kinematic motion primitives (kMPs), via trajectories learned from deep rei...

Pneumatic artificial muscles (PAMs) are linear pneumatic actuators consisting of a flexible bladder with a set of in-extensible fibers woven as a sheath on the outside. Upon application of pressure, the actuators contract or expand based on the angle of winding of the braid. Due to the similarity in properties of the actuators with biological muscl...

In this paper, we present a Monte Carlo simulation based method to determine the workspace of spatial parallel and hybrid manipulators. The method does not need the solution of the forward kinematics problem which is often difficult for spatial multi-degree-of-freedom parallel and hybrid manipulators. The method uses the solution of the inverse kin...

This paper deals with the issue of robustness in control of robots using the proportional plus derivative (PD) controller and the augmented PD controller. In literature, a variety of PD and model based controllers for multi-link serial manipulator have been claimed to be asymptotically stable for trajectory tracking, in the sense of Lyapunov, as lo...

A flexible spine is capable of bearing both transverse and axial external loads. At the same time, it is observed in animals that the spine deforms substantially during their motion and this allows the body to move efficiently and achieve high speeds. This paper deals with the modeling and design of one-dimensional flexible objects for a desired lo...

Multi-fingered hands have the capability of dexterous manipulation of grasped objects and thus significantly increase the capabilities of a robot equipped with multi-fingered hands. Inspired by a multi-jointed human finger and the hand, we propose a six-degree-of-freedom model of a three-fingered robotic hand as a parallel manipulator. Two kinds of...

The author obtained his Ph. D. in 1986 under Professor Bernard Roth. In a publication from the research, it was shown that the redundant joints in a serial robot could be used to make the end-effector linear velocity distribution isotropic. In this work we revisit those results, present recent results on how redundancy is made use of in a human arm...

Heliostats capable of tracking the sun as it moves across the sky and focusing the incident solar energy on to a central receiver tower requires a two degree-of-freedom (DOF) mechanism which can orient the mirror in the desired manner. Existing two-DOF mechanism, such as the Azimuth-Elevation (Az-EL) and the Target-Aligned (T-A), have two actuators...

Multi-fingered hands enable significantly enhanced manipulation capabilities to the robot where it is attached. As a consequence, analysis, design and development of multi-fingered hands has been of continuing interest in the robotics community. In this work, we propose a probabilistic Monte Carlo based approach to obtain the workspace of a well-kn...

McKibben actuator/ Pneumatic artificial muscle(PAM) is a soft actuator which has great potential in the field of bio-inspired robotics. Miniaturized versions of PAMs or MPAMs of less than 1.5 mm diameter are ideal actuators for developing surgical devices due to their compliance and high power to weight ratio. Accurate mathematical models to repres...

This paper deals with trajectory tracking control of a car-like robot. By exploiting the differential flatness property of the system based on the dynamics, a trajectory tracking controller using flatness-based control techniques is designed. A singularity in the system for the chosen control inputs, which does not allow direct application of feedb...

In this work, we use the Monte Carlo method in conjunction with gradient based optimization algorithms to optimally design multi-degree-of-freedom parallel manipulators and closed-loop mechanisms. The design procedure takes into account practical constraints such as joint limits and guarantees well-conditioning of the desired workspace. As a first...

Honeycomb sandwich laminates with aluminum and carbon fiber reinforce polymer (CFRP) face – sheets are widely used in spacecraft structures and aerospace industries. The damping behavior of such structures are reported to improve when the empty cells of the honeycomb core is filled with damping particles. The discrete-element-method (DEM) has been...

Damping characteristic of a honeycomb sandwich laminate is reported to improve when the empty cells of the honeycomb core are filled with damping particles. The enhancement of the damping is a result of the transfer of kinetic energy from the host structure to the damping particles through impact and friction mechanism. The energy of the damping pa...

In this paper, we propose a three-degree-of-freedom spatial parallel manipulator to track the sun in central receiver tower based concentrated solar power systems. The proposed parallel manipulator consists of three ‘legs’ each containing a passive rotary(R) joint, an actuated sliding or prismatic (P) joint and a passive spherical (S) joint and is...

The work is motivated by four-legged animals which can carry large loads on their back and also navigate through rough terrains which are inaccessible to wheeled mobile robots. Several such legged robots have been designed and built (one of them is cheetah-cub (Sprwitz et al. (2013)). Most of these robots have a rigid central structure along its pr...

Hyper-redundant snakelike serial robots are of great interest due to their application in search and rescue during disaster relief in highly cluttered environments and recently in the field of medical robotics. A key feature of these robots is the presence of a large number of redundant actuated joints and the associated well-known challenge of mot...

Video showing obstacle avoidance by 12 link planar serial robot

A rotating flexible beam undergoing large deformation is known to exhibit chaotic motion for certain parameter values. This work deals with an approach for control of chaos known as chaos synchronization. A nonlinear controller based on Lyapunov stability theory is developed and it is shown that such a controller can avoid the sensitive dependence...

Significance Theories of reinforcement learning claim that motor variability helps in motor learning and are supported by recent experimental work. In contrast, theories of motor control propose that variability is noise that needs to be suppressed. We attempt to reconcile these apparent contradictory positions. Using the formulation of the unconst...

Honeycomb sandwich laminates which are the basic structural element of spacecraft have inherently low damping. In this paper, we propose to improve the damping characteristics of such structures by adding damping particles in the cells of the honeycomb. This paper presents modeling of a cantilever beam constructed with honeycomb structure with the...

In gross motion of flexible one-dimensional (1D) objects such as cables, ropes, chains, ribbons and hair, the assumption of constant length is realistic and reasonable. The motion of the object also appears more natural if the motion or disturbance given at one end attenuates along the length of the object. In an earlier work, variational calculus...

Solar panels and large reflectors used in spacecraft are made-up of aluminum-honeycomb sandwiched between composite fiber reinforced plastic (CFRP) laminates. Owing to the small inherent damping and large area to mass ratio, such structures are susceptible to strong acoustic excitations during the initial phase of launch. In this paper we present a...

A feedback controlled robot manipulator with positive controller gains is known to be asymptotically stable at a set point and for trajectory following in the sense of Lyapunov. However, when the end-effector of a robot or its joints are made to follow a time dependent trajectory, the nonlinear dynamical equations modeling the feedback controlled r...

This paper presents the development of a sun tracking system using a 3-UPU parallel spherical “wrist” manipulator. The 3-UPU manipulator, consisting of a fixed base and an orientable platform, is actuated by three linear motors at the prismatic (P) joints and has a special geometry which makes the 3-UPU manipulator equivalent to a spherical wrist w...

This paper deals with the study of the nonlinear dynamics of a rotating flexible link modeled as a one dimensional beam, undergoing large deformation and with geometric non-linearities. The partial differential equation of motion is discretized using a finite element approach to yield four nonlinear, non-autonomous and coupled ordinary differential...

It is known in literature that a wheeled mobile robot (WMR) with fixed length axle will slip on an uneven terrain. One way to avoid wheel slip is to use a torus-shaped wheel with lateral tilt capability which allows the distance between the wheel-ground contact points to change even with a fixed length axle. Such an arrangement needs a two degree-o...

Robots with snake topology and large number of redundant degrees of freedom are extensively studied due to increased flexibility in motion planning. Such robots can navigate through narrow passages, avoid obstacles and find use in search and rescue. It is also finding increasing use in fields of medical robotics and surgery in the form of actuated...

Precise positioning of catheters during an endoscopic procedure and surgery is typically a very complex and demanding task. Once endoscope tip is stationed at a particular position, the camera is focused at a particular point. In most endoscopes, any motion of the catheter is achieved by moving the endoscope tip which results in a change in camera...

There is an increased thrust to harvest solar energy in India to meet increasing energy requirements and to minimize imported fossil fuels. In a solar power tower system, an array of tracking mirrors or heliostats are used to concentrate the incident solar energy on an elevated stationary receiver and then the thermal energy converted to electricit...

A wheeled mobile robot (WMR) will move on an uneven terrain without slip if its torus-shaped wheels tilt in a lateral direction. An independent two degree-of-freedom (DOF) suspension is required to maintain contact with uneven terrain and for lateral tilting. This article deals with the modeling and simulation of a three-wheeled mobile robot with t...

This article deals with the kinematics of serial manipulators. The serial manipulators are assumed to be rigid and are modeled using the well-known Denavit-Hartenberg parameters. Two well-known problems in serial manipulator kinematics, namely, the direct and inverse problems, are discussed, and several examples are presented. The important concept...

In concentrated solar power(CSP) generating stations, incident solar energy is reflected from a large number of mirrors or heliostats to a faraway receiver. In typical CSP installations, the mirror needs to be moved about two axes independently using two actuators in series with the mirror effectively mounted at a single point. A three degree-of-fr...

Robotic surgical tools used in minimally invasive surgeries (MIS) require miniaturized and reliable actuators for precise positioning and control of the end-effector. Miniature pneumatic artificial muscles (MPAM) are a good choice due to their inert nature, high force to weight ratio and fast actuation. In this paper, we present the development of...

In concentrated solar power (CSP) power generating stations, solar energy from a large number of mirror systems, also called heliostats, is concentrated at a receiver and the thermal energy in the solar radiation is converted to electricity. Typically, the sun’s motion is tracked by using the well-known Azimuth-Elevation method or by the Target-Ali...

Hyper-redundant systems such as snake robots, flexible manipulators, ropes and strings discretized as rigid links connected by joints can be reasonably assumed to length preserving during their motion. The resolution of the redundancy in such systems have been addressed by several researchers using least squares and other techniques in which the co...

The three-wheeled vehicle, called an "auto-rickshaw", with a four-stroke petrol, LPG or CNG engine is one of the most common and affordable means of transportation (for hire) in Indian cities. It is a small, highly manoeuvrable vehicle and ideally suited for the narrow and traffic clogged streets of urban India. Electric and hybrid vehicles are par...

An optimization based method is presented for the synthesis of adjustable spherical four-link crank-rocker mechanisms for approximate multi-path generation. The synthesis is done in two stages, �first the driving dyad of the spherical mechanism is determined and then the remaining parameters are determined. The method uses a least squares based pla...

Robotic surgical tools used in minimally invasive surgeries (MIS) require reliable actuators for precise positioning and control. Miniature pneumatic artificial muscles (MPAM) appear most suited for actuating surgical devices because of their inert nature, high force to weight ratio and fast actuation. However, MPAMs are not readily available and p...

This paper presents a study of the nature of the degrees-of-freedom of spatial manipulators based on the concept of partition of degrees-of-freedom. In particular, the partitioning of degrees-of-freedom is studied in five lower-mobility spatial parallel manipulators possessing different combinations of degrees-of-freedom. An extension of the existi...

This paper deals with an optimization based method for synthesis of adjustable planar four- bar, crank-rocker mechanisms. For multiple different and desired paths to be traced by a point on the coupler, a two stage method �first determines the parameters of the possible driving dyads. Then the remaining mechanism parameters are determined in the se...

This paper deals with the synthesis of planar and spherical adjustable four-link mechanisms whose coupler point can approximately trace two or more paths prescribed by a large number of points. A single adjustment in one of the mechanism parameters is used to approximately obtain the prescribed paths. A two stage approach is used to first determine...

We present a novel concept of a threaded fastener that is resistant to loosening under vibration. The anti‐loosening feature does not use any additional element and is based on modifying the geometry of the thread in the bolt. In a normal nut and bolt combination, the axial motion of the nut or bolt is linearly related to the rotation by a constant...