Nomination of controls of various layouts for heavy machinery.

BACKGROUND: Control selection in heavy machinery may be a problem due to the poor compatibility of the commonly-used single line of vertical levers for controls. OBJECTIVE: This study examined the effects of control arrangements on directional compatibility and participant responses in terms of choice/function of controls. METHODS: We investigated experimentally, for a number of new designs of control arrangements, the selection of controls for requested functions of four different machines: fork lift trucks, excavators, tower cranes, and telescopic cranes. Control arrangements were designed with different levels of directional compatibility and participants were requested to nominate which control was related to each of the machine motions and to make ratings of certainty of response. A second part required participants to rank the various control arrangements in terms of their compatibility. RESULTS: The in-line control arrangement was worst for each machine and increased directional compatibility improved the stereotype strength, certainty of response and ranking of control arrangement. CONCLUSIONS: Directional compatibility is the main factor in the design of control/machine output arrangements due to its effect on stereotype strength and correct selection of control of a given function.

Determining the validity of the visual field principle for designing control/display arrangements.

The Visual Field (VF) principle has been found to apply in many situations, but has not been tested under many possible conditions of operator posture with different display and control locations. In this research we used four display locations, four control locations relative to a seated operator and tested the strength of population stereotype for six different types of controls with linear displays moving either horizontally or vertically and circular displays with a neutral indicator at the 12, 3, 6 and 9 o'clock positions. Apart from several minor differences in operator responses, the VF principle held up well under all these different display/control relationships. By designing the display/control arrangement to have high stereotype strength, the direction of control movement for a given direction of indicator movement can be selected to comply with the VF principle for producing fewest errors in movement direction.

Models of the effect of teleoperation transmission delay on robot movement time.

Recent research of [Scholcover and Gillan ( 2018 )] has shown experimentally that system transmission delay has a linear effect on the time taken to perform a complex tracking task with a simple teleoperated robot. This note shows that, for the case of moving a robot through a straight path, this relationship is predicted. The result is a simple modification of Drury's law to take into account the system delay. This work extends the model for performance under intermittent illumination of Drury to the effects of fixed delays in task performance, occurring with teleoperated robots. In all cases, there was empirical evidence for the predicted linear relationship. Practitioner summary: When there is a delay in system response for robotic teleoperation between a control input and system output, movement time (MT) is increased and the increased times are linearly related to the system delay. This is true for zero and first-order control and for delays occurring before and after the control action.

Movement time and guidance accuracy in teleoperation of robotic vehicles.

Two experiments are reported on the steering of a tracked vehicle through straight-line courses and corners to determine the relationships between movement time and control accuracy with the geometry of the course, such as the vehicle width, the track width and the type of corner. For straight line tracking, Drury's law in which movement time (MT) is linear with the tracking task difficulty measure [A/(W - d)] is found to hold, where A is the distance traveled, 'W' is the track width and 'd' is the vehicle width. Performance in three types of corners (right angle, cut angle and circular) varied little, with the most important factor being the clearance (W - d) available to the operator. Collisions with boundary walls were also highly related to this factor. The reported research has strong relevance to the training of operators for urban search and rescue robots. Practitioner summary: Data for steering a real vehicle in a simulated environment of straight paths and different corner geometries showed that Drury's law holds for straight line tracking and the clearance between the widths of vehicle and track is important in steering corners. Data show clear need for training of USAR (Urban Search and Rescue) operators.

Reach/Grasp Times with Lateral Reach Obstructions.

When moving to grasp an object having adjacent obstacles that limit the space available for placing the fingers, the time for the reach/grasp is dependent on the distance of reaching and the space available for finger placement. Here we model the time taken in terms of these variables and develop mathematical models for the reach and grasp phases of the task and the location of obstacles. Data show that the movement to the target may be made under visual control and that, when the obstacles are close to the target object, a visually-controlled movement is made that is modeled by a modified form of Fitts' law. The time for the two components of the reach/grasp appear to be independent and linearly additive.

Children's Control/Display Stereotypes.

Objective The aim of this study was to determine control/display stereotypes for children of a range of ages and development of these stereotypes with age. Background Little is known about control/display stereotypes for children of different ages and the way in which these stereotypes develop with age. This study is part of a program to determine the need to design differentially for these age groups. Method We tested four groups of children with various tasks (age groups 5 to 7, 8 to 10, 11 to 13, 14 to 16), with about 30 in each group. Examples of common tasks were opening a bottle, turning on taps, and allocating numbers to keypads. More complex tasks involved rotating a control to move a display in a requested direction. Results Tasks with which different age groups were familiar showed no effect of age group. Different control/display arrangements generally showed an increase in stereotype strength with age, with dependence on the form of the control/display arrangement. Two-dimensional arrangements, with the control on the same plane as the display, had higher stereotype strength than three-dimensional arrangements for all age groups, suggesting an effect of familiarity with controls and displays with increasing age. Conclusion Children's control/display stereotypes do not differ greatly from those of adults, and hence, design for children older than 5 years of age, for control/display stereotypes, can be the same as that for adult populations. Application When designing devices for children, the relationship between controls and displays can be as for adult populations, for which there are considerable experimental data.

Control Strategy in Movements with Transmission Delay.

The strategy used by participants was studied when making movements in a Fitts movement paradigm with transmission delay between control input and display output. Fitts' law in the modified form developed by E. R. Hoffmann (1992) gave an excellent description of the data. Movement time could also be expressed as a function of the total delay time (number of submovements × transmission delay) and Fitts' index of difficulty (ID). Two types of submovement were identified, being step and drag forms. The number of step submovements was the most important in determining movement time. These were related to a move-and-wait strategy used by participants. Number of submovements increased with the level of ID and transmission delay and was linearly related to the ID and product of ID by transmission delay.

Head Rotation Movement Times.

OBJECTIVE: The aim of this study was to measure head rotation movement times in a Fitts' paradigm and to investigate the transition region from ballistic movements to visually controlled movements as the task index of difficulty (ID) increases. BACKGROUND: For head rotation, there are gaps in the knowledge of the effects of movement amplitude and task difficulty around the critical transition region from ballistic movements to visually controlled movements. METHOD: Under the conditions of 11 ID values (from 1.0 to 6.0) and five movement amplitudes (20° to 60°), participants performed a head rotation task, and movement times were measured. RESULTS: Both the movement amplitude and task difficulty have effects on movement times at low IDs, but movement times are dependent only on ID at higher ID values. Movement times of participants are higher than for arm/hand movements, for both ballistic and visually controlled movements. The information-processing rate of head rotational movements, at high ID values, is about half that of arm movements. CONCLUSION: As an input mode, head rotations are not as efficient as the arm system either in ability to use rapid ballistic movements or in the rate at which information may be processed. APPLICATION: The data of this study add to those in the review of Hoffmann for the critical IDs of different body motions. The data also allow design for the best arrangement of display that is under the design constraints of limited display area and difficulty of head-controlled movements in a data-inputting task.

Amplitude and Width Manipulations in Fitts' Paradigm: Comment on Heath et al. (2011) and Heath et al. (2016).

Heath, Weiler, Marriott, Elliott, and Binstead ( 2011 ) and Heath, Samani, Tremblay, and Elliott ( 2016 ) have claimed that there are dissociable movement times for amplitude and width manipulations in the Fitts' paradigm. This may to some extent be true, but the Heath et al. ( 2011 ) and Heath et al. ( 2016 ) data do not support that contention, as shown in this comment. It is shown that data from the research of Heath et al. is not in the range of index of difficulty where ongoing visual control would be used and hence their fits of data to Fitts' law are spurious. The data of Heath et al. ( 2011 ) for arm movements and for the primary eye saccade submovements of Heath et al. ( 2016 ) are well correlated by the ballistic movement time equation of Hoffmann ( 1981 ) and Gan and Hoffmann ( 1988 ). When the ballistic equation is used to model data for constant amplitude and constant target width conditions, the effects of the amplitude and width manipulations disappear. Other research indicates that the independent effects of movement amplitude occur due to changes in the time for the distance-covering phase of the movement.

Targeted Paced and Unpaced Movements in the Transverse and Sagittal Planes.

Five experiments are reported related to control of arm movement in the sagittal and transverse planes when making paced and unpaced movements. A single group of 12 participants and the same equipment were used in the main experiments to allow comparisons across conditions. As well as the 2 different directions of movement, there were movements that were time-constrained (as in the W. D. A. Beggs & C. I. Howarth, 1971, 1972a,b paradigm) and movements that were constrained by the ending tolerance (as in Fitts' paradigm). Results showed that, for movement times as high as 900 ms, the Schmidt and Beggs and Howarth models appeared to describe the time for movements that had time constraint. Fitts' law (P. M. Fitts, 1954 ; P. M. Fitts & J. R. Peterson, 1964) applied to movements that were constrained by final accuracy. These results were independent of whether the target was in the aiming or stopping movement direction. A new interpretation of data for movements with time constraint is presented, based on the possible number of accuracy submovements available when near the target. This model suggests that the standard deviation of hits at the target is not dependent on the time spent in reaching the target region, but largely on the time remaining in order to produce final accuracy at the target.

Subjective Estimation of Task Time and Task Difficulty of Simple Movement Tasks.

It has been demonstrated in previous work that the same neural structures are used for both imagined and real movements. To provide a strong test of the similarity of imagined and actual movement times, 4 simple movement tasks were used to determine the relationship between estimated task time and actual movement time. The tasks were single-component visually controlled movements, 2-component visually controlled, low index of difficulty (ID) moves and pin-to-hole transfer movements. For each task there was good correspondence between the mean estimated times and actual movement times. In all cases, the same factors determined the actual and estimated movement times: the amplitudes of movement and the IDs of the component movements, however the contribution of each of these variables differed for the imagined and real tasks. Generally, the standard deviations of the estimated times were linearly related to the estimated time values. Overall, the data provide strong evidence for the same neural structures being used for both imagined and actual movements.

The effect of display movement angle, indicator type and display location on control/display stereotype strength.

Much research on stereotype strength relating display and control movements for displays moving in the vertical or horizontal directions has been reported. Here we report effects of display movement angle, where the display moves at angles (relative to the vertical) of between 0° and 180°. The experiment used six different controls, four display locations relative to the operator and three types of indicator. Indicator types were included because of the strong effects of the 'scale-side principle' that are variable with display angle. A directional indicator had higher stereotype strength than a neutral indicator, and showed an apparent reversal in control/display stereotype direction beyond an angle of 90°. However, with a neutral indicator this control reversal was not present. Practitioner Summary: The effects of display moving at angles other than the four cardinal directions, types of control, location of display and types of indicator are investigated. Indicator types (directional and neutral) have an effect on stereotype strength and may cause an apparent control reversal with change of display movement angle.

Movement Integration and the One-Target Advantage.

The 1-target advantage (OTA) has been found to occur in many circumstances and the current best explanation for this phenomenon is that of the movement integration hypothesis. The author's purpose is twofold: (a) to model the conditions under which there is integration of the movement components in a 2-component movement and (b) to study the factors that determine the magnitude of the OTA for both the first and second component of a 2-component movement. Results indicate that integration of movement components, where times for one component are affected by the geometry of the other component, occurs when 1 of the movement components is made ballistically. Movement components that require ongoing visual control show only weak interaction with the second component, whereas components made ballistically always show movement time dependence on first and second component amplitude, independent of location within the sequence. The OTA is present on both the first and second components of the movement, with a magnitude that is dependent on whether the components are performed ballistically or with ongoing visual control and also on the amplitudes and indexes of difficulty of the component movements.

The Psychological Cost of Making Control Responses in the Nonstereotype Direction.

OBJECTIVE: The aim of this study was to develop a scale for the "psychological cost" of making control responses in the nonstereotype direction. BACKGROUND: Wickens, Keller, and Small suggested values for the psychological cost arising from having control/display relationships that were not in the common stereotype directions. We provide values of such costs specifically for these situations. METHOD: Working from data of Chan and Hoffmann for 168 combinations of display location, control type, and display movement direction, we define values for the cost and compare these with the suggested values of Wickens et al.'s Frame of Reference Transformation Tool (FORT) model. RESULTS: We found marked differences between the values of the FORT model and the data of our experiments. The differences arise largely from the effects of the Worringham and Beringer visual field principle not being adequately considered in the previous research. CONCLUSION: A better indication of the psychological cost for use of incorrect control/display stereotypes is given. It is noted that these costs are applicable only to the factor of stereotype strength and not other factors considered in the FORT model. APPLICATION: Effects of having controls and displays that are not arranged to operate with population expectancies can be readily determined from the data in this paper.

Stereotypes for lever-tap operation.

BACKGROUND: Lever-operated taps have become more popular and are commonly used in operating theatres, food preparation areas and where users have poor strength; however, there is very little data available for user expectations on tap operation. Thus, an experiment on dual lever-operated water tap (faucets) was conducted with the aim of for providing information for improved design. OBJECTIVE: This study aims to compare different lever-tap designs and their stereotypes adopted by the end-user to operate them also to verify the stereotypes for increasing or decreasing the water flow. METHODS: 240 participants were requested to rotate the lever tap to indicate direction for increasing and decreasing water flow with simulated hardware, using actual taps placed at the top of a simulated washbasin. Nine initial positions of the lever were used for increasing and decreasing flows, ranging from the ends of both levers facing outward from the bowl center to the ends of both levers facing inward. All levers operated in the horizontal plane. RESULTS: Strong stereotypes (greater than 80%) for several initial lever orientations were found for increasing water flow, especially when the initial lever end positions were facing outwards. However, for different initial positions at which participants were told that the water was flowing and the flow was to be decreased, no strong stereotypes existed. CONCLUSIONS: The stereotypes for increasing water flow of dual-lever taps were strong, whereas those for decreasing water flow were weak and hence the stereotype reversibility was also weak. In terms of user expectations, lever taps do not show any great advantage over cross-taps in terms of operator expectations for increasing and decreasing water flow.

Fitts' Law With An Average of Two or Less Submoves?

A number of researchers have noted that, with as few as 2 submovements (primary and corrective), the movement time versus index of difficulty (ID) data are described by Fitts' law, that is, there is a linear relationship between movement time (MT) and ID. A model is presented that shows that there may be an apparent relationship of this form between MT and ID with only 2 submovements. The model is based on the characteristics of ballistic movements and the required corrections to the endpoint of the primary submovement. The model shows the close relationship between the ballistic distance-covering phase of a movement and the consequent Fitts' law. The model is tested against several data sets and found to give a good description of the aiming process.

Critical Index of Difficulty for Different Body Motions: A Review.

K.-C. Gan and E. R. Hoffmann (1988) demonstrated that there is a clear boundary between values of Fitts' index of difficulty (ID) below which movements may be made without ongoing path corrections; above this value it was necessary to use corrections to hit a target of high ID. It is shown that this critical ID (IDcrit) value is dependent on both the body component making the movement and on the form of feedback available to the person. The arm system, having the highest ratio of muscle strength to mass moment of inertia, has the highest value of IDcrit, whereas control of the body center of mass location has the lowest value of IDcrit. It is suggested that the use of visual control to lower ID values with the larger body components is due to the longer movement times available because of the physical characteristics of these components-the time is available, and therefore it is used to make path corrections.

Effect of display location on control-display stereotype strength for translational and rotational controls with linear displays.

Experiments were designed to investigate the effects of control type and display location, relative to the operator, on the strength of control/display stereotypes. The Worringham and Beringer Visual Field principle and an extension of this principle for rotary controls (Hoffmann E.R., and Chan A.H.S. 2013). "The Worringham and Beringer 'Visual Field' Principle for Rotary Controls. Ergonomics." 56 (10): 1620-1624) indicated that, for a number of different control types (rotary and lever) on different planes, there should be no significant effect of the display location relative to the seated operator. Past data were surveyed and stereotype strengths listed. Experiments filled gaps where data are not available. Six different control types and seven display locations were used, as in the Frame of Reference Transformation Tool (FORT) model of Wickens et al. (Wickens, C.D., Keller, J.W., and Small, R.L. (2010). "Left. No, Right! Development of the Frame of Reference Transformation Tool (FORT)." Proceedings of the Human Factors and Ergonomics Society 54th Annual Meeting September 2010, 54: 1022-1026). Control/display arrangements with high stereotype strengths were evaluated yielding data for designers of complex control/display arrangements where the control and display are in different planes and for where the operator is moving. It was found possible to predict display/control arrangements with high stereotype strength, based on past data. Practitioner Summary: Controls and displays in complex arrangements need to have high compatibility. These experiments provide arrangements for six different controls (rotary and translational) and seven different display locations relative to the operator.

Circular displays: control/display arrangements and stereotype strength with eight different display locations.

Two experiments are reported that were designed to investigate control/display arrangements having high stereotype strengths when using circular displays. Eight display locations relative to the operator and control were tested with rotational and translational controls situated on different planes according to the Frame of Reference Transformation Tool (FORT) model of Wickens et al. (2010). (Left. No, Right! Development of the Frame of Reference Transformation Tool (FORT), Proceedings of the Human Factors and Ergonomics Society 54th Annual Meeting, 54: 1022-1026). In many cases, there was little effect of display locations, indicating the importance of the Worringham and Beringer (1998. Directional stimulus-response compatibility: a test of three alternative principles. Ergonomics, 41(6), 864-880) Visual Field principle and an extension of this principle for rotary controls (Hoffmann and Chan (2013). The Worringham and Beringer 'visual field' principle for rotary controls. Ergonomics, 56(10), 1620-1624). The initial indicator position (12, 3, 6 and 9 o'clock) had a major effect on control/display stereotype strength for many of the six controls tested. Best display/control arrangements are listed for each of the different control types (rotational and translational) and for the planes on which they are mounted. Data have application where a circular display is used due to limited display panel space and applies to space-craft, robotics operators, hospital equipment and home appliances. Practitioner Summary: Circular displays are often used when there is limited space available on a control panel. Display/control arrangements having high stereotype strength are listed for four initial indicator positions. These arrangements are best for design purposes.

Movement of loads with trunk rotation.

Movements with participants standing at a bench and moving loads up to 6 kg were studied, with participants using two hands to hold the load and trunk rotation in order to move the loads to specified locations. Tasks were performed with rapid ballistic movements and also with ongoing visual control. Data for ballistic movements were modelled in terms of a modified form of the (Gan, K.-C. and Hoffmann, E.R. 1988. "Geometrical conditions for ballistic and visually controlled movements." Ergonomics 5 (31): 829-839) model for ballistic movements, taking into account the inertial properties of trunk rotation. Visually-controlled movements were modelled in terms of Fitts' law and a term that allowed for the ballistic form of the first submovement of the visually-controlled movement. Practitioner Summary: Movement times to move masses up to 6 kg, for workers at a bench using trunk rotation, are given. Theoretical models fit the experimental data very well and allow prediction of movement times.