As appliance designs become more complex and feature-rich, manufacturers are looking at ways to improve the human-machine interface (HMI). While touchscreens offer intuitive operation and software flexibility, touch-activated digital switches offer refined aesthetics and better sealing. Both types of controls offer space and cost savings and have become extremely popular for many appliances and devices.

But what these touch-activated controls do not supply is tactile confirmation, and the loss of that simple quality can be detrimental to user engagement and understanding, productivity, completion of transactions, safety, and satisfaction. In some applications, the lack of tactile feedback has been enough of a problem to prevent the conversion from mechanical switches to digital controls.

The TouchSense® technology developed by Immersion Corp. permits tactile feedback to be designed into the touchscreen or digital-sensor control panel. This technology makes virtual onscreen or graphical panel buttons feel more real, creating the illusion that they are being pressed and released just like mechanical buttons, which may improve some usability problems and enhance other aspects of use.

How it works

Enlarge this picture Fig. 2. TouchSense® actuator and control board shown in relation to the touchscreen carrier, display, and assembly housing.

The technology can be used with touch controls for either portable or stationary devices. Depending on product design, the components can vary in form, but the basic architecture is the same, allowing TouchSense technology to exert high-speed control over an actuator.

In small devices, the actuator may be similar to the small pager motors used in mobile phones. For larger devices, Immersion has developed custom actuators optimized for a range of touchscreen or control-panel sizes and weights.

When the user presses a graphical button, the TouchSense system drives the actuator according to a preprogrammed tactile effect. The actuator movement supplies the perception that the graphical button moves, seeming to press and release as if it were mechanical. And, tactile effects can be synchronized with sound and display changes, creating a more engaging, multi-sensory experience. (See Fig. 1.)

By varying the frequency, waveform, amplitude, and duration of the movement, a wide range of tactile responses ares possible, supporting various user interface features:

• Graphical buttons can simulate the familiar up and down clicks of physical buttons.
• Menu items can be programmed to supply a light pulse sensation or a confirming push-back response.
• Controls can exhibit increasing or decreasing vibrations corresponding to motor or fan speed, radio volume level, lighting levels, or other parameters.
• Scrolling displays can provide a pulse as each item displays and a vibration to signal when the first or last items have been reached.

Unmistakable confirmation

Fig. 3. The Effect Selector can be displayed on the target TouchSense®-enabled touchscreen to help select tactile effects for the application.

With a TouchSense-enabled touch-activated control, it doesn’t take long for a user to understand that if a response was not felt, then the system didn’t register the selection. This immediate understanding of system state, provided through definitive confirmation or its absence, solves a number of usability problems.

Tactile feedback controls can be very effective in noisy environments where sound may be ineffective for confirming selections. In quiet settings where sound is inappropriate, such as healthcare facilities, a tactile cue supplies a quiet, yet obvious, feedback directly to, and only to, the user. Sunlight can present a visibility problem, and confirming tactile feedback can help to overcome this drawback, particularly in outdoor applications such as kiosks, ATMs, vending machines, etc. Where distractions or activity interfere with a user focusing on the control, tactile feedback can reduce the time needed to confirm selections. This would be an advantage in a hospital emergency room, for example.

Enhancing usability

The TouchSense® A100 actuator showing internal construction.

TouchSense technology not only solves problems with operating touch-activated controls in certain environments, it enhances the operational interface and the ability to supply more natural and intuitive interactions. Usability is about creating an effective human-machine interface that leads to rapid and accurate task completion or a more satisfying experience. Research has discovered that multimodal applications, which use a combination of sight, sound, and touch feedback are easier and more intuitive. Yet, in the world of digital devices and controls, touch feedback is often lost.

Giving users a matched response to their touch input promotes an easier transition from mechanical switches and keys to touchscreens or  touch-activated digital switches, and it supplies more sense of control. For many applications, digital controls with tactile feedback provide more definitive transactional or operational confirmations and can improve user satisfaction.

One way tactile feedback can be used to improve usability is to provide a distinct tactile cue consistently for each type of function. For example, one could program a different tactile effect for the functions Enter, Start, and End. The consistent cue helps inform the user of a correct selection and alert them to one they didn’t intend. Moreover, applications may offer the option for the user to select from among a variety of tactile effects that they want for particular functions, allowing a unique type of personalization.

Fast response

One more benefit of adding tactile feedback to touchscreens and digital switches is how it can be used to address system response delays. Time lags between a user’s action and the system’s reaction have a big negative impact on perceived quality. Delays cause frustration, loss of confidence, unwillingness to use the system in the future, and poor product and/or brand image. And while sound and graphics subsystems often have unpredictable time lags, the tactile feedback system can be used to help minimize delay. The system can run independently from graphics and sound and was designed to provide very fast response, which denotes quality and high value.

Flexible integration

The TouchSense® A300 actuator with enclosure.

The technology works with touchscreens and digital-switch control panels of sizes from around 2.5 in. up to 19 in. (diagonal) or larger. Integration has been successfully achieved for many product designs, and millions of devices with the technology have been shipped throughout Asia, Europe, and the U.S.

TouchSense tactile feedback system architecture includes (1) control software, either installed on an Immersion-supplied control board or embedded in the product’s main microprocessor, (2) actuator(s), either an off-the-shelf pager motor or Immersion TouchSense devices, (3) a tactile effects library, and (4) a programming interface for calling tactile effects from the host application.

If a circuit board is preferred, two types are available, for either RS-232 or USB communication. For the latter, an optional USB hub provides convenient connections to subsystems. If the embedded approach would work best, a runtime executable is provided.

Actuation

As for the choice of actuation, if a standard pager motor is to be used, Immersion can help with its selection. The company also provides design guidelines for actuator mounting and control circuitry. To actuate larger touchscreens or control panels, Immersion currently supplies two sizes of actuators, both optimized for generating high forces with small displacements. (See actuator photos.) The type and number of actuators depends on the size, weight, and implementation of the touchscreen or panel. Guidelines for positioning and mounting the actuators are flexible and allow the tactile feedback technology to be integrated in a wide range of product designs. In addition, some touchscreen implementations may require a carrier for control, which would be designed using Immersion-supplied guidelines.

Tactile Effects Library

The tactile effects library includes a wide variety of effects so that controls can be clearly distinguished and products differentiated. The TouchSense system gives designers a convenient method for choosing appropriate effects and including them in the user interface design. (See Fig. 3.)

Software-integration guidelines explain the use of a streamlined API to call the tactile effects from the host application. For some implementations, an Immersion software development kit can be used, which gives designers several programming options including a Windows ActiveX control, a cross-platform API in source code form, and communications support for custom interfaces. Sample code and a full description of the process of adding tactile feedback to the host application is also included.

To evaluate the technology for touchscreen use, demonstration units with example applications are available. The demonstrators are probably the easiest and fastest way to determine if a touchscreen with tactile feedback would improve a given product design.

Touchscreens and digital controls with tactile feedback are just beginning to come to market, but already they show much promise for improving the HMI and promoting a more intuitive, engaging, and satisfying experience for the user. 

For more information email: mlevin@immersion.com.

The TouchSense® family includes a Software Development Kit, two types of actuators, and two types of control boards, RS-232 or USB. The USB board has an optional 3-input USB hub (shown).

SIDEBAR | Potential Applications |

Large and small household appliances. Especially for often-used devices, the familiar mechanical feel that tactile feedback provides could help users adapt to and appreciate a transition from traditional to sleek and modern electronic controls.

Global positioning/navigation systems. With an immediate tactile cue, users don’t have to wait for a visual response, which can reduce glance time, helping them keep their eyes on the road.

Remote controls. A confirming tactile response can improve the usability of small buttons, especially in low-light conditions, and replace an audio cue that would detract from music or video soundtracks.

Medical diagnostic equipment. In medical facilities, where audible cues would be unsettling or disturbing to a patient, tactile feedback provides unmistakable confirmation that can let the caregiver focus more on the patient, less on the device. And with touch being the most personal of the senses, tactile feedback could be used to help extend a sense of caring in self-diagnostic equipment.

Test and measurement equipment. Tactile cues may help increase productivity, especially in noisy or distracting environments.

Portable terminals. The added confirmation that touch provides can help users multitask, more fully supporting the freedom of movement and the various activities that portability allows. It can also support faster and potentially more accurate data input.

Self-service terminals and kiosks. Tactile feedback in the self-service process provides an intuitive acknowledgement to the user that their selection has been received and service is proceeding. Giving users a matched response to their touch input supplies a greater sense of control, which can improve user satisfaction.

Game devices, media players, entertainment systems. Increased interaction through tactile feedback can supply more fun and engagement.