Haptic Applications Research Articles

Electronic Control of Pump Pressure for a Small Haptic Backhoe

AbstractThe use of haptic interfaces to control mobile hydraulic machinery has several enhancing features over traditional human-machine interfaces comprised of joysticks/levers. This paper presents and analyzes schemes for controlling pump pressure designed for coordinated haptic control. Typical of many small backhoes and excavators, the hydraulic system used on the test-bed is comprised of a constant displacement pump and proportional directional control valves. In this type of system, a main pressure regulator is needed to supply the other closed-centre valves with pressure and to dump the additional flow generated by the pump to tank. An energy-saving solution has a load-sensing pressure regulator that maintains the system pressure to a preset margin above the highest active load pressure. Using these valves for haptic applications requires closed-loop control. Applying closed-loop control to these valves can excite instabilities in the valve assembly due to complex interactions and nonlinearities in...

Flow Control for Coordinated Motion and Haptic Feedback

AbstractThe use of haptic interfaces to control mobile hydraulic machinery has several enhancing features over traditional human-machine interfaces comprised of joysticks/levers. This paper presents pressure and flow control schemes designed for coordinated haptic control. Typical of many small backhoes and excavators, the hydraulic system used on the test-bed is comprised of constant displacement pumps and proportional directional control valves. In this type of system, a main pressure regulator is needed to supply the other closed-centre valves with pressure and dumps the additional flow from the pump to tank. Using these valves for haptic applications requires accurate closed-loop control. The focus of this paper is on the flow control scheme. Performance of the proportional directional control valves are compared with and without pressure compensation. A velocity feedback loop is present in order to improve the accuracy of the control system. A small input dead-zone function is proposed in order to pr...

Neural-Network-Based Contact Force Observers for Haptic Applications

In the majority of robotic and haptic applications, including manipulation and human-robot interaction, contact force needs to be monitored and controlled. Transparent implementation of bilateral teleoperation or haptic controllers necessitates the exchange of operator and environment contact forces. This requires the use of expensive commercially available force/torque sensors, which are rather bulky, are vulnerable to impact forces, and increase system inertia and compliance. An alternative solution is the use of dynamic force observers, which estimate external forces using system dynamic model. However, due to the uncertainties in system dynamic structure and parameters, these model-based observers do not produce accurate force estimates, and often create a dynamic lag that may cause bandwidth limitation and instability. This paper proposes two neural-network-based force/torque observers that do not require a system dynamic model. The observers can estimate human hand force and environment contact force with up to 98.3% accuracy in the sense of mean-square error, and with negligible dynamic lag. The performance of the proposed observers are extensively analyzed in separate human-robot and robot-environment experimental settings, and in a two-channel bilateral teleoperation control loop with multiple runs with two Planar Twin-Pantograph haptic devices

Modeling context in haptic perception, rendering, and visualization

Haptic perception refers to the ability of human beings to perceive spatial properties through touch-based sensations. In haptics, contextual clues about material,shape, size, texture, and weight configurations of an object are perceived by individuals leading to recognition of the object and its spatial features. In this paper, we present strategies and algorithms to model context in haptic applications that allow users to haptically explore objects in virtual reality/augmented reality environments. Initial results show significant improvement in accuracy and efficiency of haptic perception in augmented reality environments when compared to conventional approaches that do not model context in haptic rendering.

From measured physical parameters to the haptic feeling of fabric

Abstract real-time cloth simulation involves the solution of many computational challenges, particularly in the context of haptic applications, where high frame rates are necessary for obtaining a satisfactory tactile experience. In this paper, we present a real-time cloth simulation system that offers a compromise between a realistic physically-based simulation of fabrics and a haptic application with high requirements in terms of computation speed. We place emphasis on architecture and algorithmic choices for obtaining the best compromise in the context of haptic applications. A first implementation using a haptic device demonstrates the features of the proposed system and leads to the development of new approaches for haptic rendering using the proposed approach.

Haptic applications for molecular structure manipulation

We describe the application of haptic technology to enhance the information available in chemical systems, specifically related to computational drug design. These methods are designed to build upon the visual information presented by molecular viewers and add the sensation of touch, or force feedback. The addition of sensory input can aid in the analysis of molecular structures and the understanding of intermolecular interactions by delivering chemically relevant forces to the end user.

Enabling design and interactive selection of haptic modes

The ever increasing size and complexity of volumetric data in a wide range of disciplines makes it useful to augment volume visualization tools with alternative modalities. Studies have shown that introducing haptics can significantly increase both exploration speed and precision. It is also capable of conveying material properties of data and thus has great potential to improve user performance in volume data exploration. In this paper we describe how recent advances in volume haptics can be used to build haptic modes—building blocks for haptic schemes. These modes have been used as base components of a toolkit allowing for more efficient development of haptic prototypes and applications. This toolkit allows interactive construction, configuration and fine-tuning of both visual and haptic representations of the data. The technology is also used in a pilot study to determine the most important issues and aspects in haptic volume data interaction and exploration, and how the use of haptic modes can facilitate the implementation of effective haptic schemes.

Editorial: design of haptic user-interfaces and applications

This special issue focuses on the design of haptic (touchbased) user-interfaces and applications. Devices that provide haptic feedback are increasingly being used in all manner of applications to provide an improved dialogue between a computer interface and a user. The use of the sense of touch allows a new range of applications to be targeted, and for existing interactions to take new forms. The scope of haptic applications now looks set to grow further, with the release of significantly lower cost haptic devices within the price range of individuals or small institutions. Much of the work in the area until now has been on the engineering of devices and perceptual issues, both fundamental to the development of the topic. However, we are now at a stage where we can begin to think about how best to design haptic interfaces, interactions and experiences from a user’s point of view. This is crucial if we are to get users to accept and use haptic technology. There is also a need to develop heuristics and guidelines for the use of haptics to allow new groups of developers and designers to create effective haptic experiences. This special issue begins to explore the relationships between haptic devices, human perception and computer applications.

Real-Time subspace integration for St. Venant-Kirchhoff deformable models

In this paper, we present an approach for fast subspace integration of reduced-coordinate nonlinear deformable models that is suitable for interactive applications in computer graphics and haptics. Our approach exploits dimensional model reduction to build reduced-coordinate deformable models for objects with complex geometry. We exploit the fact that model reduction on large deformation models with linear materials (as commonly used in graphics) result in internal force models that are simply cubic polynomials in reduced coordinates. Coefficients of these polynomials can be precomputed, for efficient runtime evaluation. This allows simulation of nonlinear dynamics using fast implicit Newmark subspace integrators, with subspace integration costs independent of geometric complexity. We present two useful approaches for generating low-dimensional subspace bases: modal derivatives and an interactive sketching technique. Mass-scaled principal component analysis (mass-PCA) is suggested for dimensionality reduction. Finally, several examples are given from computer animation to illustrate high performance, including force-feedback haptic rendering of a complicated object undergoing large deformations.

Torque Control of Electrorheological Fluidic Resistive Actuators for Haptic Vehicular Instrument Controls

Force-feedback mechanisms have been designed to simplify and enhance the human-vehicle interface. The increase in secondary controls within vehicle cockpits has created a desire for a simpler, more efficient human-vehicle interface. By consolidating various controls into a single, haptic feedback control device, information can be transmitted to the operator, without requiring the driver’s visual attention. In this paper, the experimental closed loop torque control of electro-rheological fluids (ERF) based resistive actuators for haptic applications is performed. ERFs are liquids that respond mechanically to electric fields by changing their properties, such as viscosity and shear stress electroactively. Using the electrically controlled rheological properties of ERFs, we developed resistive-actuators for haptic devices that can resist human operator forces in a controlled and tunable fashion. In this study, the ERF resistive-actuator analytical model is derived and experimentally verified and accurate closed loop torque control is experimentally achieved using a non-linear proportional integral controller with a feedforward loop.

Comparative study and experimental verification of singular-free algorithms for a 6 DOF parallel haptic device

It is well known that there exist many more singularities in parallel type mechanisms compared to serial type mechanisms. In haptic applications, these singularities deteriorate the force reflecting performance. Furthermore, as opposed to general manipulators, haptic systems cannot avoid the singular point, since they are operated by the user’s random motion command. Although many singularity-free algorithms for kinematically redundant manipulators have been proposed, singularity-free algorithms for parallel haptic application have not been extensively discussed. In this paper, various singularity-free algorithms that are appropriate for parallel haptic systems will be discussed. A new 6 degree-of-freedom (DOF) parallel mechanism equipped with four sub-chains is designed and employed as the test device. To cope with the singularity problem, four task-priority algorithms and a redundant actuation algorithm are introduced and compared through simulation. In addition, experiments have been performed to show the effectiveness of those algorithms at the presence of singularity.

Haptic state surface interactions

Haptic state-surface interaction techniques, which encode modes into force states, make interactions with 3D objects more fluid and natural. Our techniques comprise only a subset of those necessary to support a fully functional haptic application with capabilities similar to a drawing program such as Adobe Illustrator. However, these techniques can potentially simplify some common operations, such as editing points on a curve.

Flexible tactile sensor technology: bringing haptics to life

The continued evolution of computer technology requires us now more than ever to investigate and understand man‐machine interfaces. Physical interface peripherals such as touch‐screens and force feedback systems demand a comprehension of the tactile forces involved. To accomplish this, flexible, easy‐to‐install, minimally intrusive sensors are essential. Thanks to the development of such sensors, many doors have been opened for innovative haptic applications in a variety of fields including medicine, manufacturing, and entertainment.

Virtual DesignWorks—designing 3D CAD models via haptic interaction

Haptic devices (force feedback interfaces) show great promise for use in the design of CAD models. However, current haptic systems are used primarily to verify rather than to interact with CAD systems to design a model. The paper discusses a haptic-based CAD system—Virtual DesignWorks. It is the world's first haptic application for the design of CAD models based on component technology (COM+). With haptic devices, the system allows engineers, in virtual space, to directly touch a native B-Rep CAD model, and deform it by pushing, pulling and dragging its surfaces in a natural three-dimensional environment. Virtual DesignWorks adopts the novel COM-based haptic model, which demonstrates significant advantages compared to the traditional haptic models. Force feedback gives designers the greatest flexibility for the design of complex surfaces, and haptics has the potential to become a critical interface for design applications.

Modeling of a Magnetorheological Actuator Including Magnetic Hysteresis

Magnetorheological (MR) actuators provide controlled torque through control of an applied magnetic field. Therefore knowledge of the relationship between the applied current and output torque is required. This paper presents a new nonlinear modeling of MR actuators considering magnetic hysteresis to determine the torque-current nonlinear relationship. Equations for transmitted torque are derived according to mechanical shear configurations of the MR actuator. Hodgdon's hysteresis model is used to capture the characteristics of hysteresis nonlinearity in the MR actuators. An MR actuator test setup has been constructed using a commercial MR brake to evaluate the proposed model. The measured torque shows hysteresis effects as the current increases and decreases. Using Hodgdon's hysteresis model of the magnetic circuit and Bingham model of the MR fluid, a novel nonlinear model of the MR actuator is obtained as a torque estimator for practical torque control purpose. The validity of the theoretical results is verified by comparison between experiments and simulations. Furthermore, the current versus torque frequency response of the MR actuator is examined to evaluate its applicability to torque control. The bandwidth of the MR actuator is high enough for especially haptic applications.

6자유도 병렬형 햅틱장치의 설계와 특이점 회피 알고리즘의 비교연구

It is known that parallel-type mechanisms have many singularities than serial-type mechanisms. In haptic application, these singularities deteriorate the system performance when the haptic system displays the reflecting force. Moreover, different from general manipulators, haptic systems can't avoid the singular point because they are operated by user's random motion command. Although many singularity-free algorithms for serial mechanisms have been proposed and studied. singularity-free algorithms for parallel haptic application have not been deeply discussed. In this paper, various singularity-free algorithms, which are appropriate to parallel haptic system, will be discussedand evaluated.

Haptic interaction with virtual objects: the technology and some applications

Haptics is an emerging technology that allows touch‐enabled interaction with virtual objects. Analogous to the use of computer graphics for rendering of a three‐dimensional (3D) scene to give the user a visual description of the scene, it is possible to use computer haptics to let the user touch objects in the 3D scene. This is normally accomplished by having the haptics engine sending either force vectors or positional information to a haptics device, a robotic arm, that the user manipulates. The purpose of this paper is to give an overview of this technology, describe haptic devices and haptic application programming interfaces. We will also illustrate the use of haptics technology by describing a few industrial and medical applications.

Don't Take Touch for Granted: An Interview with Susan Lederman

Susan Lederman (SL) is an invited member of the International Council of Research Fellows for the Braille Research Center and a Fellow of he Canadian Psychology Association. She was also an Associate of the Canadian Institute for Advanced Research in the Robotics and Artificial Intelligence Programme for 8 years. A Professor in the Departments of Psychology and Computing & Information Science at Queen's University at Kingston (Ontario, Canada), she has written and coauthored numerous articles on tactile psychophysics, haptic perception and cognition, motor control, and haptic applications in robotics, teleoperation, and virtual environments. She is currently the coorganizer of the Annual Symposium a Haptic Interfaces for Teleoperation and Virtual Environment Systems. René Verry (RV) is a psychology professor at Millikin University (Decatur, IL), where she teaches a variety of courses in the experimental core, including Sensation and Perception. She chose the often-subordinated somatic senses as the focus of her interview, and recruited Susan Lederman as our research specialist.

Spatial trajectories and reaction times of aimed movements: effects of practice, uncertainty, and change in target location.

1. The spatial and temporal characteristics of arm movements in two (X-Y) dimensions were studied in three rhesus monkeys a) during the acquisition of an aiming motor skill, b) under conditions of spatial and temporal uncertainty, and c) when the location of the target changed during the reaction or movement time, from 50 to 400 ms after the presentation of the target. 2. The acquisition of the aiming skill was marked by an exponential reduction in the spatial variability of the movement trajectories. The reaction time remained virtually unchanged, whereas the peak velocity increased by a small amount. The skill was transferred appreciably to the other hand within a short period of training. 3. Handpath variability increased under conditions of spatial uncertainty. Temporal uncertainty in target presentation had no effect. Reaction time did not change significantly in either condition. 4. Change of target location during the reaction or movement time elicited a graded movement toward the first target, followed by reversal of direction and movement to the second target. The duration of the movement toward the first target was a linear function of the time that elapsed from the presentation of the first target to the change of targets (interstimulus interval, ISI): the later the change occurred, the longer the movement toward the first target. In contrast to the gradation of hand movement with change in target location, the eyes always fully made a saccade to the first or second target. 5. The trajectory of the initial hand movement deviated occasionally toward the second of the two targets when the interstimulus interval was short and the targets were adjacent. 6. No marked delays were observed, beyond the reaction time, when responding to the first or the second target. A large increase in peak velocity was attained after reversing the movement, i.e., on the way to the second target. 7. The results of this study indicate that the process that generates the aimed movement becomes less variable with practice and is influenced by the uncertainty of the subject about the location of the target but not by the time of its appearance. 8. The orderly modification of the movement produced by change in target location suggests that the aimed motor command is emitted in a continuous, ongoing fashion as a real-time process that can be interrupted at any time by the substitution of the original target by a new one. The effects of this change on the ensuing movement appear promptly, without delays beyond the usual reaction time. No appreciable “psychological refractory period” is observed under these conditions, and the second stimulus has continual and effective access to the process generating the aimed arm movement,