Manual Control Tasks Research Articles

Acquisition of control skill with delayed and compensated displays.

The difficulty of mastering a two-axis, compensatory, manual control task was manipulated by introducing transport delays into the feedback loop of the controlled element. Realistic aircraft dynamics were used. Subjects' display was a simulation of an "inside-out" artificial horizon instrument perturbed by atmospheric turbulence. The task was to maintain straight and level flight, and delays tested were representative of those found in current training simulators. Delay compensations in the form of first-order lead and first-order lead/lag transfer functions, along with an uncompensated condition, were factorially combined with added delays. Subjects were required to meet a relatively strict criterion for performance. Control activity showed no differences during criterion performance, but the trials needed to achieve the criterion were linearly related to the magnitude of the delay and the compensation condition. These data were collected in the context of aircraft attitude control, but the results can be applied to the simulation of other vehicles, to remote manipulation, and to maneuvering in graphical environments.

Effects of duration and vibration on performance of a continuous manual control task

An experiment is described in which two independent groups of seated subjects performed a pursuit tracking task for 202·5 min on two separate occasions. For one group, the total duration included 180 min exposure to vertical z-axis, whole-body random vibration with a bandwidth of 1 octave centred on 4 Hz. The weighted acceleration magnitude was 1·4 ms−2 r. m. s., with a crest factor of 4·13. Using the procedures denned in British Standard 6841 (BSI 1987), the motion had a vibration dose value of 20 ms−1·75. The other group received no vibration exposure. Results showed that performance declined as function of duration, but that vibration exposure did not impair performance or interact with the effect of duration. Performance in the second sessions showed less effect of duration than in the first session. The effect of duration was associated with change in both linear and non-linear tracking behaviour. Closed loop system transfer functions showed both reduced moduli and increased phase lags with increasin...

The effects of background visual roll stimulation on postural and manual control and self-motion perception.

The effects of background visual roll stimulation on postural control, manual control, and self-motion perception were investigated in this study. In the main experiment, 8 subjects were exposed to wide field-of-view background scenes that were tilted and static, continuously rotating, or sinusoidally rotating at frequencies between 0.03 and 0.50 Hz, as well as a baseline condition. The subjects performed either a postural control task (maintain an upright stance) or a manual control task (keep an unstable central display horizontally level). Root-mean square (RMS) error in both the postural and manual control tasks was low in the static tilt condition and extremely high in response to continuous rotation. Although the phases of the postural and manual responses were highly similar, the power and RMS error generated by the sinusoidal visual background stimulation peaked at a lower frequency in the postural task. Vection ratings recorded at the end of the postural and manual trials somewhat paralleled the frequency tuning differences between tasks, which a subsequent experiment showed to be the result of the differential motion of the central display rather than the differential positioning of the subject. In general, these results show that the dynamic characteristics of visual orientation systems vary according to the specific motor and/or perceptual system investigated.

Effects of whole-body vibration waveform and display collimation on the performance of a complex manual control task : R. W. McLeod and M. J. Griffin 1990 Aviation, Space and Environmental Medicine61(3), 211–219. (9 pages, 7 figures, 3 tables, 23 references) (in English)

An experiment is described in which two independent groups of eight subjects each performed a combined continuous and discrete tracking task during exposure to vertical whole-body vibration. Both groups received sinusoidal and random vibration at preferred third-octave centre frequencies of 0.5-10 Hz. One group performed the task with the display collimated by a convex lens. Without the collimation, performance was disrupted by both types of vibration at all vibration frequencies; collimation removed the disruption at frequencies above 1.6 Hz. There were differences in the effects of random and sinusoidal vibration at 2.0 and 2.5 Hz, suggesting that compensatory eye movements were assisting performance during exposure to the predictable sinusoidal motion. The results show that continuous control performance was disrupted by visual interference at frequencies above 1.6 Hz; closed-loop system transfer functions showed that visual interference increased the phase lags which impaired control performance. Possible mechanisms explaining the disruption in performance at lower frequencies are discussed.

Experimental studies of manual optimization in control tasks

The abilities of a human operator have been examined experimentally in a manual control task. In these experiments, a human operator was instructed to control the output of a plant so as to minimize a performance index shown after each trial. The performance index, a combination of control effort and plant results, allows the operator to improve performance after repeated trials. The human operator can do the task satisfactorily after enough training even if there is no information about the plant dynamics or the form of the performance index. In addition, the operator develops distinct control action depending on the distinct characteristics of the performance index. Results are presented for both linear and nonlinear plants. The results indicate the high-level abilities of a human operator in controlling plants based on given performance indices. The high-level abilities include both learning and becoming an excellent controller.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Ergonomics : R. W. McLeod and M. J. Griffin 1988 31(8), 1193–1203. Performance of a complex manual control task during exposure to vertical whole-body vibration between 0·5 and 5·0 Hz. (11 pages, 2 figures, 2 tables, 15 references) (in English)

Ergonomics : R. W. McLeod and M. J. Griffin 1988 31(8), 1193–1203. Performance of a complex manual control task during exposure to vertical whole-body vibration between 0·5 and 5·0 Hz. (11 pages, 2 figures, 2 tables, 15 references) (in English)

Review of the effects of translational whole-body vibration on continuous manual control performance

A review of the literature concerned with experimental studies of the effects of translational whole-body vibration on continuous manual control performance is presented. Results from studies of the effects of vibration variables (vibration frequency, magnitude, axis, random vibration and multi-axis vibration) are compared. Evidence of the influence of control system variables (physical characteristics of the control, control gain, system dynamics and display variables) is also provided. Studies of the effects of vibration duration on manual control performance are reviewed separately. A behavioural model is presented to summarize the mechanisms (including vibration breakthrough, visual impairment, neuro-muscular interference and central effects) by which whole-body vibration may interfere with the performance of continuous manual control tasks. The model emphasizes the adaptive ability of the human operator.

Cooperative synthesis of control and display augmentation

The cooperative control synthesis technique, previously developed to synthesize control augmentation so as to optimize the human operator's subjective rating, is extended to the synthesis of display augmentation for closed-loop manual control tasks. The procedure allows for simultaneously augmenting the display dynamics as well as plant or controlled element dynamics via feedback, and explicitly includes task-related and pilot-centered requirements in the design objectives. Connections are made between the proposed technique and classical manual control theory, and the new methodology is demonstrated by considering a compensatory tracking task for a generic controlled element. Analytical evaluations of the various control and display augmentation results and comparisons with the results of previous experimental studies are discussed.

Performance of a complex manual control task during exposure to vertical whole-body vibration between 0.5 and 5.0 Hz.

An experiment is described in which seated subjects performed first-order pursuit tracking with a simultaneous discrete task; performance with the discrete task was dependent on performance of the continuous task. Vertical, z-axis, whole-body sinusoidal vibration was presented at frequencies from 0·5 to 5·0Hz at an acceleration magnitude of 2·0 ms−2 r.m.s. in three separate sessions. In the first session, inter-subject and intra-subject variability masked any disruption caused by the vibration. After further training, all vibration frequencies disrupted performance of the continuous task. Disruption was independent of vibration frequency below 3·15Hz and increased at 4·0 and 5·0Hz. A visual mechanism was assumed to account for the increased disruption at these higher frequencies. Mechanisms which may have been responsible for the disruption below 3·15 Hz are discussed. Effects of vibration on the discrete task were attributable to disruption in performance of the continuous task. The results illustrate th...

Speech variability effects on recognition accuracy associated with concurrent task performance by pilots

Abstract Pairs of pilots performed an aircraft warning classification task using an isolated-word speaker-dependent speech recognition system to record their responses. Task-induced stress was manipulated by means of different scoring procedures for the warning classification task and by inclusion of a competitive manual control task (Voorhees and Bucher 1984, Voorhees and Bucher 1985). High quality tape recordings were made of pilots’ speech spoken to the recognizer while performing under the different types of task loading. This speech was then analysed spectrographically for timing differences in the pilot's manner of speaking as a function of task loading, and of recognition accuracy associated with different types of task loading. Recognition errors were recorded by type for an isolated-word speaker-dependent system and by an off-line technique for a connected-word speaker-dependent system. While recognition errors increased with task loading for the isolated word system, there was no such effect for task loading when tape recordings of the same utterances were recognized by a connected word system. The results suggest areas for further improvements to speaker-dependent recognition algorithms and provide predictions of the types of recognition errors that can be expected with current recognition technology used by pilots under moderate to high levels of task loading.

Normalized predictive deconvolution - A time series algorithm for modeling human operator dynamics

A time series technique is presented for identifying the dynamic characteristics of the human operator in manual control tasks from relatively short records of experimental data. Control of the system excitation signals used in the identification is not required. The approach is a multichannel identification technique for modeling multi-input/multioutput situations. The method presented includes statistical tests for validity, is designed for digital computation, and contains a new method for the determination of model order. A comprehensive relative power spectral density analysis may also be performed for validated models and the frequency response may be estimated for the operator. This method is applied to several sets of experimental data where the results are discussed and shown to provide considerable insight into overall system behavior. New results are also presented for a multi-input task that has not been previously modeled to demonstrate the strengths of the method.

Voice and Manual Control in Dual Task Situations

This paper describes various influences of compatibility and task-resource competition that affect time-sharing a verbal and a manual control task, with either manual or voice control. In the reported experiment subjects performed a 2-dimensional discrete tracking task concurrently with a Sternberg memory search task. Each task was controlled either by voice, the left hand, or the right hand. The major influence on performance was the advantage for conditions in which the Sternberg task was voice-controlled and tracking was manually controlled. Voice-controlled tracking produced incompatibility, while bimanual control produced resource competition. Smaller, but still reliable effects were observed for hemispherically-compatible assignments (left-handed tracking).

Toward a unifying theory for aircraft handling qualities

A structural model of the human pilot that has been used to study a variety of problems in manual control tasks is applied to the study of aircraft handling qualities. A physical theory for handling qualities is reviewed and interpreted in terms of the model. The theory postulates that, in manual control tasks, rate-control activity on the part of the human is the sole determining factor in the generation of pilot opinion ratings. Using the structural model, rate-control activity is related to the power in a proprioceptive feedback signal proportional to vehicle output-rate due to control input. By appealing to single-axis tracking tasks, the model and theory are shown capable of demonstrating the manner in which three major determinants of aircraft handling qualities can effect pilot opinion ratings. A brief comparison with a handling qualities metric derived from the optimal control model is made.

An Optimization Model of Self-Paced Tracking

A model which describes human performance in a self-paced tracking task was developed based on the notion that human operators are intermittent-acting or sampled-data servo-mechanisms. The model had a functional form in terms of the probability of success and failure resulting from the execution of a manual control task such as drawing a line between fixed boundaries. The human operator was modelled as an optimizer, balancing costs and penalties of speeds and errors to achieve a maximum expected payoff. The performance of the model was evaluated by simulating a line drawing task on a digital computer. Model predictions obtained via simulation were compared with the data collected from human subjects performing the actual task in a laboratory setting. The predictions of the model were confirmed, suggesting that human operators can in fact be modelled as optimizers when performing a manual control task.

Suppression of biodynamic disturbances and pilot-induced oscillations by adaptive filtering

A method for reducing the effects of biodynamic interferences due to whole-body vibrations is described. Manual control tasks are particularly addressed. The method, based on adaptive filtering, enables a substantial attenuation of additive stick involuntary control commands due to pilot body vibrations (stick feedthrough). By means of computer simulations the feasibility of the proposed filtering method is demonstrated for two examples 1) adaptive filtering of biodynamic interferences due to stick feedthrough in manual vehicular control, 2) suppression of pilot-induced oscillations (PIO) due to stick feedthrough. This form of PIO is particularly anticipated for flexible aircraft having a high-gain, stiff stick. It is demonstrated that adaptive filtering is capable of suppressing the biodynamic interferences without substantially affecting the control characteristics of the aircraft/pilot system.

Visual Scan and Performance — Indicators of Man's Workload?

The feasibility of the concept of the human as an information processing channel and its performance in terms of trans informat ion was studied in a three-axis compensatory manual control task for the evaluation of four different display configurations. Two experiments are described in which the exnerimental parameters were 1) tracking bandwidth in input random tracking and controlled element dynamics and 2) additional load of subjects by a visual or auditory side task. The study describes an investigation of the relationship between the subjects' eye-scan behaviour and their performance level. The findings are confirmed by the measures on subjective effort expressed in terms of the standard deviations of the control stick signals.

Experimental Design of a Model for the Dynamic Behaviour of Pilot Candidates

The dynamic behaviour of man in closed two-variable control loops can be approximated satisfactorily by a quasilinear model. For uncoupled systems and the transmission channel eye-hand a data acquisition procedure has been developed, which supplies frequency responses of the human controller. The dynamic behaviour of human controllers has been examined with the aid of a tracking simulator with stochastic disturbances as input signal. The input and output signals have been sampled and recorded by a process computer and evaluated by means of correlation and Fourier analysis on a larger computer system. The results of the evaluations allow conclusions on the capability of pilot candidates to solve manual control tasks.

Mathematical Concepts for Modeling Human Behavior in Complex Man-Machine Systems

Many useful mathematical models for manual control, monitoring, and decision-making tasks in man-machine systems have been designed and successfully applied. However, critical comments have occasionally been made, mainly by practitioners concerned with the design of complex man-machine systems. They especially blame models which seem to explain only data from abstract subtask experiments designed particularly for these models. In this review paper, an initial approach to bridging the gap between these two perspectives of models is presented. From the manifold of possible human tasks, a very popular baseline scenario has been chosen, namely car driving. A hierarchy of human activities is derived by analyzing this task in general terms. A structural description leads to a block diagram and a timesharing computer analogy. The range of applicability of existing mathematical models is considered with respect to the hierarchy of human activities in real complex tasks. Also, other mathematical tools so far not often applied to man-machine systems are discussed. The mathematical descriptions at least briefly considered here include utility, estimation, control, queueing, and fuzzy set theory as well as artificial intelligence techniques. Some thoughts are given as to how these methods might be integrated and how further work might be pursued.

Digital Man-Machine Control Systems: The Effects of Preview Lag

Previous studies have clearly demonstrated the benefit of providing the human operator with input preview information during manual control tasks. This study was designed to analyse if and to what extent such preview benefit depends on whether the preview extends immediately ahead of the ‘ present’ position or is postponed (lagged) by a certain amount. The experimental results from eight subjects performing a purely digital pursuit control task with a first-order controlled system showed that the performance deteriorated (RMS error increased) nearly linearly with increasing preview lag for a band-limited white Gaussian noise input. However for a first-order autoregressivc process (with parameter α =0·9) as reference input, the control performance was clearly less affected by the preview lag. Irrespective of the extent of the preview lag, performance was clearly superior for α equals; 0·9 as compared to α =o,

A system for the assessment of human performance in concurrent verbal and manual control tasks

A multipurpose laboratory system incorporating a voice interactive terminal and graphic display system is described. The facility is designed to investigate some aspects of human performance on concurrent verbal and tracking tasks. The results of a pilot study showing decrements in dual-task performance are reported.