Display And Control

DESIGN AND ARRANGEMENT OF DISPLAYS AND CONTROLS SITI ZAWIAH MD DAWAL DEPT OF ENG. DESIGN AND MANUFACTURE UNIVERSITY OF MALAYA

Displays and controls are the interface through which human-machine information exchange takes place. The design of the displays and controls of a machine can either facilitate interaction or increase task difficulty and the probability of error.

CONTROLS Controls transmit input to a piece of equipment. Usually operated by hand or foot. The results of the control inputs are shown to the operator either in terms of displays or indicators or by the ensuring actions of the machine.

DESIGN OF CONTROLS Controls should be designed to be operable in low-stress postures and without static loading of body parts, particu-larly the fingers. Control dimensions should be determined using appropriate hand and foot anthropometry and a knowledge of the mechanical advantage needed to enable the user to actuate the control easily.

Vehicle Controls Steering wheels, joy sticks, and pedals are commonly used to control vehicles. Control usability can be affected by the resistance of the control, which should be operable using forces which are a fraction of the operator's maximum voluntary contraction. However, the control should offer some resistance to movement so that bumping errors and muscle tremor do not cause control errors (Young, 1973).

Control Distinctiveness In many instances, numerous controls are grouped together on a panel and the designer's task is to ensure that operators can easily distinguish between different controls. In addition, manual controls provide the operator with tactile feedback which can be used to give a distinctive identity to a control or related set of controls.

McCormick and Sanders (1982) recommend using several dimensions to code different controls so as to enhance their distinctiveness. Designers may choose from shape, color, texture, size, location, operational method, position, and labeling.

Voice Control: Problems and prospects The development of speech-recognition technology introduces the possibility of using voice as a control device. Some potential advantages of voice control are the following: 1. It provides an extra communication channel which may take some of the load off more conventional channels. 2. It frees the hands to carry out other activities. 6. Subroutines are already built up for the production of voice commands, so training time should be reduced.

The processing requirements for issuing voice commands would not be expected to conflict with those for manual control; therefore voice is often thought to have the potential to speed up task performance or increase an operator's information-handling capacity.

Some evidence for this comes from Martin and Long (1984), who investigated a simulation of a ship's gunfire control task which involved compensatory tracking as a primary task. They found that a simultaneous pointing task degraded tracking performance, whereas a spoken version of the same task did not. It was concluded that the findings were consistent with a multichannel model of performance in which speech and tracking occupied parallel, but independent, channels with no common capacity limitation.

Voice Recognizer Faces Speech is a complex acoustic signal containing bands of energy centered on 500, 1500, 2000, and 3000 Hz. These are known as formants and they consist of an initial transient segment followed by a steady-state segment. The lower two formants are sufficient for the perception of speech, which enables bandwidth compression to be implemented to reduce the information load of speech transmission systems and speech synthesizers.

Many investigations of speech perception by humans have been carried out by researchers in the field of psycholinguistics (see Howard, 1983, for an introduction to this research). Speech perception is thought to depend on the interplay of both top-down and bottom-up processes. Bottom-up (analytic) processes detect particular features in the speech signal as it is received.

Combinations of features detected in speech form the characteristic signatures of basic speech sounds such as phonemes, syllables, or words. When matched with a stored representation of known features, the speech can be said to have been recognized. Top-down (synthetic) processes use higher-order information to synthesize possible items which can be matched against the incoming signal (trying to "guess what's coming next"). A knowledge of grammar, syntax, and context is required to drive these higher order interpretive processes.

DISPLAYS Display provide operator with information about the status of equipment. Displays are either visual, auditory, tactile. Labels and instructions or warnings are special kind of displays.

Selecting the display Status information Historical information Predictive information Instructional information Commanding information

VISUAL DISPLAY Check display Qualitative display Quantitative display

SCALES AND POINTERS May be straight, curved or circular Should be simple Numerals

CODING Location Shape Size Mode of operation Labeling Color

Combining control and display

Use Grouping Principle in Panel Design

Avoid Spatial Transformations

COMPUTER INPUT DEVICES Numerical Keypads Computer keyboards Other input devices

LABELS It is necessary to use label to locate , identify, read or manipulate controls, displays or other equipment. Labeling must be done so that the information provided accurately and rapidly.

DESIGN OF LABELS Orientation –horizontal –easy to read Location – place near item it identifies Standardization -consistently Abbreviation -common Brevity –concise as possible –intended meaning Familiarity –words familiar Visibility and Legibility – can be read easily –under worst illumination, vibration…etc

WARNINGS Reasons to warn – potential injury, danger What to warn about – people must be warn about various concerns –e.g product must be used properly.. Whom to warn – product manufacturer has the duty to warn –potential user, customer, sales marketing How to warn –on product itself, advertizing sales instructions to customers/ users

DESIGN OF WARNINGS Visual warning –may contain text, graphics pictures – often redundant Symbol and Icons –meant to identify object , warn of hazard or indicate an action.