Haptic Technology
By: Sayali Nehul, Sudhanshu Nikalje, Sanket Nikam, Rucha Pansare, Harshawardhan Patil.
- Introduction –
Haptic technology refers to technology that interfaces the user with a virtual environment via the sense of touch by applying forces, vibrations, and/or motions to the user. This mechanical stimulation may be used to assist in the creation of virtual objects (objects existing only in a computer simulation), for control of such virtual objects, and to enhance the remote control of machines and devices (teleoperators). This emerging technology promises to have wide reaching applications as it already has in some fields. For example, haptic technology has made it possible to investigate in detail how the human sense of touch works by allowing the creation of carefully controlled haptic virtual objects. These objects are used to systematically probe human haptic capabilities, which would otherwise be difficult to achieve. These new research tools contribute to our understanding of how touch and its underlying brain functions work. Although haptic devices are capable of measuring bulk or reactive forces that are applied by the user, it should not to be confused with touch or tactile sensors that measure the pressure or force exerted by the user to the interface.
In short haptic technology deals with tactile feedback which recreates sense of touch by applying force, vibrations, or motion to the user .Using mechanical simulation virtual objects in computer can be created and can also be used to carry telerobotics .It does for the sense of touch what graphics has done for vision .Haptic feedback also provides measure of force exerted by the user on an interface .Thus it provides a crucial insight to how human sense of touch works.
The two important criteria involved are haptics rendering and visual rendering that indicate the virtual environment’s information to the human user .Haptics rendering includes software’s based on algorithms to find where the point of contact has taken place and the forces between the virtual environment and the user .Visual rendering uses algorithms to compute real time behaviour of virtual environment graphics using mathematical modelling techniques.
The word haptic, from the Greek word haptikos, means “tactile, pertaining to the sense of touch”. Simple haptic devices are common in the form of game controllers, joysticks, and steering wheels.
2. Working of haptic technology –
To understand the basic working of haptics, consider the following diagram:
Basically a haptic system consist of two parts namely the human part and the machine part. In the figure shown above, the human part (left) senses and controls the position of the hand, while the machine part (right) exerts forces from the hand to simulate contact with a virtual object. Also both the systems will be provided with necessary sensors, processors and actuators. In the case of the human system, nerve receptors performs sensing, brain performs processing and muscles performs actuation of the motion performed by the hand while in the case of the machine system, the above mentioned functions are performed by the encoders, computer and motors respectively.
Basically the haptic information provided by the system will be the combination of –
(i) Tactile information
(ii) Kinaesthetic information.
Tactile information refers the information acquired by the sensors which are actually connected to the skin of the human body with a particular reference to the spatial distribution of pressure, or more generally, tractions, across the contact area. For example when we handle flexible materials like fabric and paper, we sense the pressure variation across the fingertip. This is actually a sort of tactile information.
Kinaesthetic information refers to the information acquired through the sensors in the joints. Interaction forces are normally perceived through a combination of these two information’s.
3. Haptic rendering –
Haptic rendering is the process of generating and computing forces in response to the user’s interaction with the virtual object. The process of interacting with the virtual object has been of great interest to many researchers worldwide. Rendering refers to a process by which desired stimuli are imposed on a user to convey the information about the virtual object. New technology always amazes people and just as the people were amazed to see the computers a few decades back, people are amazed to feel the virtual objects today. Haptic rendering is one of the most important parts of the haptic interfaces as, better the haptic rendering better the virtual feel. To enhance the haptic rendering various rendering algorithms are implemented.
As shown in the above figure, the haptic rendering algorithm forms the most important integral part of the haptic system. The haptic rendering algorithm generally consists of two sub-algorithms, collision detection algorithm and collision response algorithm. As the user changes his position or the force feedback (shown in figure) the change in position or orientation is acquired and the Collision Detection algorithm detects the collision between the fingertip and the virtual environment. If a collision is detected, then the Collision Response algorithm calculates the force of interaction between the user and the virtual environment and then instructs the response device to generate the required force, thus generating the actual representation of the virtual object. The update rate of the haptic feedback loop must be at least 1 KHz, in order to maintain the feel of the virtual object. The Object Database should be maintained so that all the physical properties of the object can be replicated correctly in the virtual environment. Moreover calculation of the contact forces is equally important than just calculating the collisions. Thus, better the haptic rendering algorithm, better the imitation of the real environment.
4. Haptic feedback –
Haptic / Tactile feedback (or haptics) is the use of advanced vibration patterns and waveforms to convey information to a user or operator. Haptic feedback has two major benefits for manufacturers. Firstly, it can improve user experience. Even everyday products are now being built with touch displays and interfaces. They’re cheaper to construct than control panels with buttons or switches, and designers can make context specific user interfaces simply by changing the graphical layout on the screen.
Haptic feedback for a Virtual Reality (VR) application –
Virtual reality (VR) applications strive to simulate real or imaginary scenes with which users can interact and perceive the effects of their actions in real time. Ideally the user interacts with the simulation via all five senses. However, today’s typical VR applications rely on a smaller subset, typically vision, hearing, and more recently, touch.
Figure below shows the structure of a VR application incorporating visual, auditory, and haptic feedback.
The application’s main elements are:
1) The simulation engine, responsible for computing the virtual environments behaviour over time.
2) Visual, auditory, and haptic rendering algorithms, which compute the virtual Environment’s graphic, sound, and force responses toward the user.
3) Transducers, which convert visual, audio, and force signals from the Computer into a form the operator can perceive.
The human operator typically holds or wears the haptic interface device and perceives audiovisual feedback from audio (computer speakers, headphones, and so on) and visual displays (for example a computer screen or head-mounted display).Whereas audio and visual channels feature unidirectional information and energy flow (from the simulation engine toward the user), the haptic modality exchanges information and energy in two directions, from and toward the user. This bi-directionality is often referred to as the single most important feature of the haptic interaction modality.
5. Haptic Devices –
A haptic device is the one that provides a physical interface between the user and the virtual environment by means of a computer. This can be done through an input/output device that senses the body’s movement, such as joystick or data glove. By using haptic devices, the user can not only feed information to the computer but can also receive information from the computer in the form of a felt sensation on some part of the body. This is referred to as a haptic interface
These devices can be broadly classified into:-
1. Virtual reality/ Tele-robotics based devices-
a. Exoskeletons and Stationary device
b. Gloves and wearable devices
c. Point-source and Specific task devices
d. Locomotion Interfaces
2. Feedback devices-
a. Force feedback devices
b. Tactile displays
6. Commonly used haptic interfacing devices –
1. Phantom –
It is a haptic interfacing device developed by a company named Sensible technologies. It is primarily used for providing a 3D touch to the virtual objects. This is a very high resolution 6 DOF device in which the user holds the end of a motor controlled jointed arm. It provides a programmable sense of touch that allows the user to feel the texture 9and shape of the virtual object with a very high degree of realism. One of its key features is that it can model free floating 3 dimensional objects.
2. Cyber glove –
The principle of a Cyber glove is simple. It consists of opposing the movement of the hand in the same way that an object squeezed between the fingers resists the movement of the latter. The glove must therefore be capable, in the absence of a real object, of recreating the forces applied by the object on the human hand with (1) the same intensity and (2) the same direction. These two conditions can be simplified by requiring the glove to apply a torque equal to the interphalangian joint.
3. Cyber Grasp –
The Cyber Grasp is a full hand force-feedback exo skeletal device, which is worn over the Cyber Glove. Cyber Grasp consists of a lightweight mechanical assembly, or exoskeleton, that fits over a motion capture glove. About 20 flexible semiconductor sensors are sewn into the fabric of the glove measure hand, wrist and finger movement. The sensors send their readings to a computer that displays a virtual hand mimicking the real hand’s flexes, tilts, dips, waves and swivels. The same program that moves the virtual hand on the screen also directs machinery that exerts palpable forces on the real hand, creating the illusion of touching and grasping. A special computer called a force control unit calculates how much the exoskeleton assembly should resist movement of the real hand in order to simulate the onscreen action. Each of five actuator motors turns a spool that rolls or unrolls a cable. The cable conveys the resulting pushes or pulls to a finger via the exoskeleton.
7. Application of Haptic technology –
1. Graphical User Interfaces –
Video game makers have been early adopters of passive haptics, which takes advantage of vibrating joysticks, controllers and steering wheels to reinforce on-screen activity. But future video games will enable players to feel and manipulate virtual solids, fluids, tools and avatars. Graphical user interfaces, like those that define Windows and Mac operating environments, will also benefit greatly from haptic interactions. Imagine being able to feel graphic buttons and receive force feedback as you depress a button. Some touch screen manufacturers are already experimenting with this technology.
2. Haptics For Medical And Visual Disabilities –
Haptic interfaces for medical simulation have proved very useful .Touch and kinaesthesia are subtle , effortless senses which are important for fast ,accurate interaction with our environment .These prove to be very crucial for minimal invasive procedures .These include laparoscopy ,interventional radiology and remote surgery .In open surgery , surgeons rely heavily on touch to distinguish healthy tissue from disease infected tissue. The advantage of using haptics technique is that surgeons can perform large number of similar operation with less fatigue .Also in ophthalmology, the supporting springs that hold artificial lens within lens capsule after removal of cataract are done via haptics .Furthermore the virtual haptic feedback is useful for palpatory diagnosis that means detection of medical problem through touch .Recent technology based on haptics is also utilised in fields of prosthetics.
3. Haptics in teleoperation –
Teleoperation means operation of a machine situated at a distance .It is very similar to a remote control but is usually seen in research, academics, and technical environment .Although it is usually associated with robotics and mobile robots, it can still be applied to a machine or a device which a person is operating from a distance. Haptics has led to an increase in precision of teleoperation by force and surface information feedback .Force feedback is obtained by sending back pressure and force through haptic devices at the point of interest .Such applications find use in assistive surgical robotics .They are also used in simulators to train medical and military personnel .In assistive robotic surgery it is possible to carry a precise surgical procedure that will improve and hence shorten the healing process.
4. Haptics in cars –
For the past two model years, the BMW 7 series has contained the iDrive (based on Immersion Corp’s technology), which uses a small wheel on the console to give haptic feedback so the driver can control the peripherals like stereo, heating, navigation system etc. through menus on a video screen.
8. Limitations –
There are some of limitations associated with haptics, which, if overcome, can cause haptics to bring about a revolution .Some of the limitations are:
i. Haptics being a new technology requires a very high initial investment and hence is very costly.
ii. The haptic devices are usually bulky .These devices are large in size and greater in weight which become a big problem in case of wearable haptic devices.
iii. Haptic interfaces exert forces with limited magnitude and not equally well in all directions.
iv. Haptic rendering algorithm which provides the virtual environment operates in discrete time whereas the realtime users operate in continuous time.
v. Bandwidth limitation is a major problem associated with haptics .Data transmission has limited bandwidth .Haptic data is usually heavy which requires greater bandwidth .If this bandwidth is not available this may lead to wrong interpretation.
vi. Universal operability of haptic interfaces: Haptic interfaces are developed for specific applications .For a new task, some new implementations are required .This adaptation can be tedious .Hence a uniform universally accepted interface is required.
vii. Instability and vibration : Graphic rendering requires updates at the rate of 60 Hz .But haptic update rates must be of 1000Hz .If the required updates rates are not met, this may lead to instability .Thus the system may become unstable .
9. Conclusion –
Haptics is still in its nascent stage. It has immense potential to bring about drastic improvements in our interactions with the virtual world. However, it does have a few limitations in hardware, development cost, and its implementation. Day by day, the cost of technology is decreasing. Haptics is finding applications in every possible field such as education, entertainment, art, medical, teleoperation .Haptics has a very large future scope in every possible field .With an increase in investments in terms of money, time, dedication and space haptics is bound to revolutionize the world.
