There has always been something appealing about a simple knob as a control input. Its operation is familiar and intuitive. And on an electromechanical control, a knob typically provides enough resistance to let the user know positively that a function has been actuated or selected.

The use of rotary encoders took the evolution of the knob to the next level, combining a familiar input device with the benefits of electronic controls. That advance, however, sacrificed the tactile response users had experienced when turning electromechanical controls and placed a heavier reliance on auditory and visual feedback. Recently, another advance in the realm of rotary input has not only restored tactile feedback for the user, but also taken it a giant leap forward by providing an entire menu of tactile feedback effects that are programmable.

This new programmable rotary encoder enables a flexible, intelligent design solution for today’s user interface — and an alternative to electromechanical switches and conventional encoders. Developed by Immersion Corp., San Jose, Calif., the TouchSense PR-1000 encoder can be programmed to supply users with a variety of touch feedback options, depending on the context of operation. It can change its characteristics in real time, in response to dynamic system parameters. Given its multifunction capability, designers may be able to reduce the number of controls to save space and improve aesthetics. In some cases, inventory, design, and installation costs can be reduced. Leveraging the sense of touch can help enhance productivity, ease of use, safety, ergonomics, and user satisfaction.

Possible uses

Barrier. Sensation of hitting a hard stop. Barrier effects restrict the user’s motion and are useful for indicating first and last items, minimum and maximum, or the edge of an area.

A multifunction encoder that emulates several types of controls, including functions such as detents, stops, hills, and varying levels of friction or force, can intuitively guide users through various stages of operation. For consumer appliances, touch feedback can be effective when designers wants to add functionality without increasing complexity, or when they want to provide a system status where none existed before.

A rotary control with variable detents (clicks) and push-to-select function can be used to reduce control clutter for combination settings, such as temperature/weight/time/cooking mode or temperature/washing mode/fabric type. Where the appliance doesn’t visually indicate its setting, such as a ceiling fan, the programmable encoder can communicate this information through touch feedback.

Compound. Two or more effects such as barriers and detents. A compound effect, like small detents with a deeper center detent and barriers on both sides, would be appropriate for a balance control, for example. Compound effects help designers closely match tactile sensations to operational steps, which can enhance usability.

Where a product has entirely new features or functions —building, accessing, and managing a music or video library, for example — a multifunction encoder can help the designer create an intuitive, streamlined interface incorporating menu control, scroll, and select functions. Because the encoder is digitally controlled, it can provide dynamic response, changing the list length and adding a detent whenever the user loads a new video, for example. Because touch feedback is such a new medium for the appliance user-interface, its power to communicate and guide may not be immediately evident or understood. Would it add value to a security system? A power tool? A sewing machine? A satellite radio? The answers likely depend on how the user interacts with the system and what information needs to be communicated back to the user. It is also important to consider that, along with sight and sound, touch is one of the crucial senses people use for so many tasks, from peeling an orange to signing documents. In fact, touch provides several higher-order advantages for the user.

Touch makes sense

Constant Force. Continuous force independent of position. Constant force can be used to simulate dynamics such as gravity, friction, or momentum.

Touch provides reflex-rate response and allows precise control and discrimination. With touch feedback, users can easily verify engagement or completion and intuitively understand continuous monitoring and progress. Touch feedback can be used to reduce visual strain, especially for exacting or prolonged tasks. A gentle resistance can make it easier to control motion and to identify discrete elements or boundaries.

Touch can reduce cognitive loading and the need for focused attention. Joining touch with sight and sound enlarges the multimodal experience, resulting in a sensory combination that can enhance even very simple tasks and provide a satisfying, confirming, congruent experience. When users can also rely on their sense of touch, they can often perform tasks faster, more precisely, and with greater confidence. Alternately, for some functions, tactile cues can offset or replace reliance on sight or sound.

Detent. Notches associated with selection position. Used to mark fine or coarse increments or selections, detents can be customized in size, shape, and number to suit context-sensitive requirements.

Establishing context

Hill. A plateau style of wide detent. A hill effect could be used for menu wraparound, letting the user know they have moved from last to first menu item. A hill can also be used to indicate a return from a submenu back to the main menu or to signal the crossing of a boundary.

Context-sensitivity can be used to streamline an interface. For example, a programmable rotary encoder can be configured as a five-position selector switch, and later, a control that produces a hill effect to signal when a boundary has been crossed. Unlike conventional electromechanical controls, the TouchSense encoder provides a two-way channel of communication. It supplies a position input to the system and functions as a touch feedback output device. Designers can configure the encoder to perform within the context of operation as the user may naturally expect for tasks such as:

• Adjusting parameters: low to high, magnitude, volume, brightness, speed.
• Varying ratio settings: balance, fade, treble/bass.
• Selecting discrete items: on/off, an item in a list of options.
• Choosing nonlinear settings: arbitrary and changing parameters irregularly spaced along a scale.
• Navigating a layered hierarchy: a menu tree.
• Scrolling selections: long, short, and dynamic lists.
• Making precision adjustments: fine or coarse gain.

Control Consolidation

In addition to context-sensitivity, multifunction controls offer space saving advantages to minimize clutter and improve aesthetics. The PR-1000 encoder saves space behind the panel, as well, measuring just 1.26 in. in diameter and less than 1 in. in depth.

Because one encoder can be implemented as many different controls, including dials, scroll wheels, and levers, part numbers in inventory can be reduced. With this type of control consolidation, there also may be opportunities for reduced wiring time and costs.

Programmability

Touch feedback effects can be dynamically controlled, providing for a consistent interface even for highly interactive applications, such as when the user controls items in a list (the video library). Even for static interfaces, the effects can be quickly evaluated and refined so that final decisions can be made later in the design process.

Further, programmable encoders can be modified in the field, allowing upgrades. Reinforcement of the manufacturer’s brand is possible because the feel of the control can be consistently recreated. Programmability may also allow manufacturers to provide that most sought after of user benefits — personalization — by supplying user configurable settings for the feel or action of the control.

System Architecture

Tactile effect files are created using Immersion developer software and stored in an effect library, which can be called by the host application. Upon receiving position or selection information from the encoder, the application updates the user interface, determines the need for control action, and communicates those actions to the encoder through a serial protocol.

The embedded microprocessor interprets these messages and initiates tactile effects by sending control signals to the encoder’s actuator. The microprocessor also updates the encoder’s rotary position and sends the information back to the host application.

The encoder’s braking actuator dissipates energy and resists user motion. This braking system produces a detent by applying the braking actuator as the user turns the encoder’s shaft to enter the detent effect. At the top of the peak, the braking actuator releases, which gives the sensation of falling into the detent.

The encoder produces a barrier effect by applying the brake, which sharply stops further rotation in that direction. Designed for easy panel mount installation, the encoder can be configured for dial, scroll wheel, thumb wheel, lever, or T-handle devices, and can include a push-to-select function. It comes ready to install and can be integrated into a wide variety of control panels and systems. The native communications protocol is TTL serial; however other common protocols, such as CAN, RS-232, or USB, can be supported.

Developer Tools

Windows-based Immersion Studio for PR-1000 software lets programmers define and experience the encoder’s tactile effects, modify effect parameters, and save the corresponding register values to an electronic file. When an encoder is connected to the host computer, any change to a parameter is downloaded to the device registers, allowing design changes to be immediately experienced.

Tactile effect parameters include shape, width, amplitude, and number of detents, as well as the type and strength of bounding conditions. Immersion offers a detailed programming guide that illustrates the types of effects that can be created for the PR-1000 encoder and explains how to define effects to be played in real time. A developer kit includes sample encoders, a communication interface board supporting USB and RS-232, and cables for prototyping purposes. The company also offers customized training and support for product design, integration, and application development.

A dynamically programmable touch feedback device is a sophisticated design tool that provides product manufacturers a way to stand out from the competition, showcase product functionality in a whole new manner, balance functional richness with ease of use, or reduce control clutter.

Touch Feedback Benefits

User benefits may include:

• Reflex-rate response.
• Unmistakable confirmation, fast verification.
• Easy discrimination.
• Intuitive understanding.
• Reduced visual strain, especially for exacting or prolonged tasks.
• A richer, more satisfying, multisensory experience.<

Manufacturer benefits may include:

• Control consolidation for inventory reduction, space savings, simplified installation.
• Flexibility to make design decisions later, faster.
• Dynamic response to user interaction.
• Field upgradeability.
• Brand reinforcement and opportunity for personalization.
• Context sensitivity and precision control.