Mehrdad Hosseini Zadeh

Perception-based lossy haptic compression considerations for velocity-based interactions

The ability of technology to transmit multi-media is very dependent on compression techniques. In particular lossy compression has been used in image compression (jpeg) audio compression (mp3) and video compression (mpg) to allow the transmission of audio and video over broadband network connections. Recently the sense of touch or haptics is becoming more important with its addition in computer games or in cruder applications such as vibrations in a cell phone. As haptic technology improves the ability to transmit compressed force sensations becomes more critical. Most lossy audio and visual compression techniques rely on the lack of sensitivity in humans to pick up detailed information in certain scenarios. Similarly limitations in the sensitivity of human touch could be exploited to create haptic models with much less detail and thus requiring smaller bandwidth. The focus of this paper is on the force thresholds of the human haptic system that can be used in a psychophysically motivated lossy haptic (force) compression technique. Most of the research in this field has measured the just noticeable difference (JND) of the human haptic system with a human user in static interaction with a stationary rigid object. In this paper our focus involves cases where the human user or the object are in relative motion. An example of such an application would be the haptic rendering of the user’s hand in contact with of a high-viscous material or interacting with a highly deformable object. Thus an approach is presented to measure the force threshold based on the velocity of the user’s hand motion. Two experiments are conducted to detect the absolute force threshold (AFT) of the human haptic system using methodologies from the field of psychophysics. The AFTs are detected for three different ranges of velocity of the user’s hand motion. This study implies that when a user’s hand is in motion fewer haptic details are required to be stored calculated or transmitted. Finally the implications of this study on a more complete future study will be discussed.

Human Factors for Designing a Haptic Interface for Interaction with a Virtual Environment

Designing haptic displays is one of the main challenges in creating virtual reality systems with the sense of touch. The design of the hardware and software of haptic interfaces depends critically on the capabilities of the human haptic system. For example, force feedback interfaces, due to inherent hardware limitations such as friction and actuator saturation, present forces to users in the case of interactions with a virtual environment which are only approximations of the forces that they would feel if they were interacting with the real world. Thus, quantitative human studies are required to obtain the impact on human performance of these approximations in the forces from the haptic devices. First, the focus of this paper is on the quantitative measures of human factors (force thresholds) that affect the design specifications of force feedback haptic interfaces when the human user or the object are in relative motion. Second, the effects of two direction of forces and the increment/decrement of forces are also studied through two experiments. It appears that the JNDs of human force perception depend on the force direction and the force increment/decrement, and these two variables must be incorporated in an efficient haptic design technique when the users hand is in motion.

Automatic Vehicle Parallel Parking Design Using Fifth Degree Polynomial Path Planning

Automatic vehicle parallel parking design and its related concerns about safety improvement remain some of the heated problems for automatic land vehicular control. This paper presents the calculation process of a parallel parking cars path planning and the algorithm development for its motion design based on a fifth-degree polynomial curve. In addition to the proposed algorithm for automatic vehicle parking, the minimum horizontal distance allowed for parking between a car and a parking spot is also investigated. The preliminary results show that the fifth degree polynomial path planning and the algorithm are well applied to the automatic parallel parking problem.

Design of a Tactile Instrument to Measure Human Roughness Perception in a Virtual Environment

This paper presents the experimental results on the measurement of human texture perception in virtual environments. The experiment is conducted with a haptic tactile instrument that provides sensations of rough textures directly to the fingertip of the users. It consists of a brush and a DC motor. The brush rubs directly against the users fingertip. Simulated texture is felt through an aperture on the tactile actuator where the users place their fingertip. The speed and direction of the brush are varied to control the roughness of the virtual surface and to determine the effect of either variable on perceived roughness. The actuator is designed to be attached to an existing force feedback device in order to create an interface that can provide force feedback and tactile feedback. The magnitudes of rough textures are measured through this device by comparing the virtual textures with real sandpapers of different grit sizes. Through human factor testing, it is found that the direction of rotation has negligible effects on roughness perception when the time gap between two consecutive stimuli is as large as 10 s. However, when the time gap is reduced to 0.5 s, the effects of direction become prominent. The just noticeable difference with respect to speed is found to decrease as the base speed of the brush increases. The results also show that although each subjects perception of roughness is biased using various sandpapers, the measured data is divided between two trends. One group of users perceives the roughness to increase with increasing speed, while the other group perceives the roughness to decrease.

Sensorless resistive-based control of shape memory alloy actuators in locking mechanism

This article presents a sensorless resistive-based control method to control shape memory alloy wire actuators to be used in the development of a laparoscopic surgical locking system. Shape memory alloy wire electrical resistance is measured to control the martensite phase fraction of shape memory alloy wire. The martensite phase fraction is calculated based on mathematical heating model, resistance models, and the measured resistance. Experiments are conducted to evaluate the validity and performance of the method in the control of the locking system angle. The results show that the sensorless resistive-based control method accurately controls the wire without using any position sensors, resulting in the lower cost, size, and weight of the system. The results show very small steady-state errors, verifying the practicability of this method. The sensorless resistive-based control method has the potential to be used in many applications in which cost and space are limited and the use of an external sensor is impossible or costly.

Providing haptic feedback in robot-assisted minimally invasive surgery: A direct optical force-sensing solution for haptic rendering of deformable bodies

Abstract This paper presents an enhanced haptic-enabled master-slave teleoperation system which can be used to provide force feedback to surgeons in minimally invasive surgery (MIS). One of the research goals was to develop a combined-control architecture framework that included both direct force reflection (DFR) and position-error-based (PEB) control strategies. To achieve this goal, it was essential to measure accurately the direct contact forces between deformable bodies and a robotic tool tip. To measure the forces at a surgical tool tip and enhance the performance of the teleoperation system, an optical force sensor was designed, prototyped, and added to a robot manipulator. The enhanced teleoperation architecture was formulated by developing mathematical models for the optical force sensor, the extended slave robot manipulator, and the combined-control strategy. Human factor studies were also conducted to (a) examine experimentally the performance of the enhanced teleoperation system with the optical force sensor, and (b) study human haptic perception during the identification of remote object deformability. The first experiment was carried out to discriminate deformability of objects when human subjects were in direct contact with deformable objects by means of a laparoscopic tool. The control parameters were then tuned based on the results of this experiment using a gain-scheduling method. The second experiment was conducted to study the effectiveness of the force feedback provided through the enhanced teleoperation system. The results show that the force feedback increased the ability of subjects to correctly identify materials of different deformable types. In addition, the virtual force feedback provided by the teleoperation system comes close to the real force feedback experienced in direct MIS. The experimental results provide design guidelines for choosing and validating the control architecture and the optical force sensor.

Design of a haptic display for interacting and sliding on deformable objects

We present a stable and robust point-based haptic rendering methods to interact with various types of deformable elastic object, from (soft) low-stiff to (rigid) high-stiff, using control algorithms. The proposed method offers a high-fidelity 3D force reflecting haptic model to guarantee a stable sliding and force (feedback) field over the surface of polygonal-based deformable bodies with different normal stiffness in each triangle mesh. Control algorithms are examined to maintain and to improve the stability margins and achievable performances for the haptic display with force continuity. Two classes of control strategies are investigated. The first is a lead-lag (L-L) compensator designed based on classical control and the second scheme is a linear-quadratic-Gaussian (LQG) controller designed from modern control theory. Detailed comparison and evaluation of the proposed methods are presented to illustrate the performance of the haptic display when applied for deformable objects.

Design and evaluation of a haptic tactile actuator to simulate rough textures

This paper presents the design of a tactile actuator that creates rough textures directly at the fingertip of the user. The purpose of the tactile actuator is to convey varying magnitudes of surface roughness to the users. The stimulus is created by a rotating spiral brush. The results of a psychophysical experiment show that the speed of the brush is directly related to roughness perception. However, there are two groups of users that perceive roughness in an opposite manner from each other.

Active blind spot crash avoidance system: A haptic solution to blind spot collisions

Blind spots are a nuisance of everyday driving that cause a significant number of accidents every year. Current blind spot systems mainly take advantage of visual feedback for the driver. However, an active blind spot system physically involves the driver to help reduce the number of overall accidents. In this paper, a force-feedback gas pedal and a force-feedback steering wheel are used in conjunction with a driving simulator to improve upon existing blind spot detection and avoidance systems. Preliminary human testing results show that by adding an active blind spot crash avoidance system to the already visual blind spot light can help to reduce the number of collisions.

Factors Affecting the Perception-Based Compression of Haptic Data

The ability of technology to transmit multi-media content is very dependent on compression techniques since bandwidth affects how much information can be transmitted in a given amount of time. Researchers have investigated efficient lossy compression techniques for image compression (jpeg) (Miano J., 1999), audio compression (mp3) (Brandenburg K., 1999; Gersho A., 1994) and video compression (mpg) (Bhaskaran V., Konstantinides K., 1999) to facilitate the storage and transmission of audio and video. Recently, haptics is becomingmore important with its addition in various applications such as computer-aided design (CAD), tele-surgery, rehabilitation, robot-assisted surgery, and graphical user interfaces (GUI) to name a few. Haptic technology enables computer users to touch and/or manipulate virtual or remote objects in simulated environments or tele-operation systems. If haptic cues (e.g. touch sensations) are displayed in addition to visual and auditory cues, these VEs are called haptic-enabled virtual environments (HEVEs) (Srinivasan M. and Basgodan C., 1997). If haptic data is to be stored, transmitted and reproduced, the efficient use of the available bandwidth and computational resources is a concern. Most lossy audio and visual compression techniques rely on the lack of sensitivity in humans to pick up detailed information in certain scenarios. Similarly, haptic perception-based lossy compression techniques utilize limitations in the sensitivity of human touch to create haptic models with much less detail and thus requiring less bandwidth for a given sensation. Essentially, perception-based approaches use the threshold or just noticeable difference (JND) of force perception to develop efficient compression techniques. Force JND is the minimum difference that we can notice between two forces: the base force and an increment/decrement of the base force (Gescheider G.A., 1997). The haptic data would be stored or sent over the network when the value of sampled force data was greater than the force threshold value. It is thus necessary to quantify the force threshold and to investigate the impact of important factors on the force threshold. Most of the research in this field studied force perception with a human user in static interaction with a stationary rigid object (Hinterseer et al., 2005, 2006). It is equally important to 28