Isometric Joystick Research Articles

A Cortical Mechanism Linking Saliency Detection and Motor Reactivity in Rhesus Monkeys.

Sudden and surprising sensory events trigger neural processes that swiftly adjust behavior. To study the phylogenesis and the mechanism of this phenomenon, we trained two male rhesus monkeys to keep a cursor inside a visual target by exerting force on an isometric joystick. We examined the effect of surprising auditory stimuli on exerted force, scalp electroencephalographic (EEG) activity, and local field potentials (LFPs) recorded from the dorsolateral prefrontal cortex. Auditory stimuli elicited (1) a biphasic modulation of isometric force, a transient decrease followed by a corrective tonic increase, and (2) EEG and LFP deflections dominated by two large negative-positive waves (N70 and P130). The EEG potential was symmetrical and maximal at the scalp vertex, highly reminiscent of the human "vertex potential." Electrocortical potentials and force were tightly coupled: the P130 amplitude predicted the magnitude of the corrective force increase, particularly in the LFPs recorded from deep rather than superficial cortical layers. These results disclose a phylogenetically preserved corticomotor mechanism supporting adaptive behavior in response to salient sensory events.Significance Statement Survival in the natural world depends on an animal's capacity to adapt ongoing behavior to abrupt unexpected events. To study the neural mechanisms underlying this capacity, we trained monkeys to apply constant force on a joystick while we recorded their brain activity from the scalp and the prefrontal cortex contralateral to the hand holding the joystick. Unexpected auditory stimuli elicited a biphasic force modulation: a transient reduction followed by a corrective adjustment. The same stimuli also elicited EEG and LFP responses, dominated by a biphasic wave that predicted the magnitude of the behavioral adjustment. These results disclose a phylogenetically preserved corticomotor mechanism supporting adaptive behavior in response to unexpected events.

Development of motor coordination during joint action in mid-childhood

The ability to act jointly with others is a hallmark of primate evolution and is fundamental for human development. In recent years, the study of coordination strategies between individuals performing joint actions has received growing attention. However, when, in the course of post-natal development, this cognitive-motor function emerges is still unknown. Here, we studied dyads of peers aged 6–9 years, as well as adult subjects, while they performed a task where the same action, namely, exerting hand force on an isometric joystick to move a visual cursor from a central toward a peripheral target, was performed in a “solo” and in a social “cooperative” context. The results revealed that during joint action planning, an attempt to synchronize one's own action with that of a partner emerges at 7 years of age, together with a reduction in the duration and variability of the reaction times. A critical time is 8 years, when “solo” performance reaches a high level of accuracy. From this age, another coordination strategy, based on the online monitoring of the peer's behavior, seems to be implemented during the execution of joint action. The motor and cognitive development occurring during childhood are discussed as possible mechanisms mediating, respectively, the capability and the propensity to take into account the peer's behavior for implementing a common action plan.

Do non-human primates cooperate? Evidences of motor coordination during a joint action task in macaque monkeys

Humans are intensively social primates, therefore many of their actions are dedicated to communication and interaction with other individuals. Despite the progress in understanding the cognitive and neural processes that allow humans to perform cooperative actions, in non-human primates only few studies have investigated the ability to interact with a partner in order to reach a common goal. These studies have shown that in naturalistic conditions animals engage in various types of social behavior that involve forms of mutual coordination and cooperation. However, little is known on the capacity of non-human primates to actively cooperate in a controlled experimental setting, which allows full characterization of the motor parameters underlying individual action and their change during motor cooperation. To this aim, we analyzed the behavior of three pairs of macaque monkeys trained to perform solo and joint-actions by exerting a force on an isometric joystick, as to move an individual or a common cursor toward visual targets on a screen. We found that during cooperation monkeys reciprocally adapt their behavior by changing the parameters that define the spatial and temporal aspects of their action, as to fine tune their joint effort, and maximize their common performance. Furthermore the results suggest that when acting together the movement parameters that specify each actor's behavior are not only modulated during execution, but also during planning. These findings provide the first quantitative description of action coordination in non-human primates during the performance of a joint action task.

Advanced Joystick Algorithms for Computer Access Tasks

ObjectiveTo compare 2 correction algorithms and 2 joysticks (a conventional movement-sensing joystick and a custom-designed isometric joystick) in computer access tasks. DesignRepeated-measures, within-subject. SettingNational Veterans Wheelchair Games. ParticipantsFifteen participants with various diagnoses including multiple sclerosis, spinal cord injury, traumatic brain injury, Wilson disease, and Parkinson disease. MethodsA computer access test scenario was used to evaluate the effects of applying proportional integral derivative (PID)–based and least means–based algorithms to suppress unintentional cursor motions by users with upper extremity spasticity. Main Outcome MeasuresTrial completion time, reaction time, and trajectory-based measures: movement offset, movement variability, and percentage of out-of-path motion on test tracks. ResultsThe quantitative outcome measures showed a high correlation with clinical measures for spasticity and functional independence. On small test tracks, compared to when no correction algorithms were used, both algorithms performed equally well in suppressing unintentional cursor motions. On longer test tracks, participants navigated most accurately while using the PID algorithm. Participants moved the cursor more accurately using the isometric joystick compared to the movement-sensing joystick, with only a slight increase in the task completion times. ConclusionsThe joysticks and the advanced correction algorithms show promise for use in wide-ranging applications as control interfaces.

Tuning Algorithms for Control Interfaces for Users with Upper-Limb Impairments

Approximately 40% of Americans with disabilities cannot operate wheeled mobility devices and computers adequately because of diminished upper-limb motor control, sensory limitations, and cognitive impairments. We developed tuning software that can customize control interfaces for individuals with upper-limb impairments. This study compared the differences in each parameter among different diagnostic groups. The age of the subjects ranged from 18 to 80 yrs. The participants were classified into the following groups: athetoid cerebral palsy, spastic cerebral palsy, multiple sclerosis, upper-limb spasticity, and control. We used a validated tuning software protocol to customize an isometric joystick before a virtual tracing or driving task. Tuning parameters were then compared across groups. Seventy-five subjects were included. Gain, the parameter responsible for force-to-output ratios, in each directional axis (leftward gain: P = 0.018; rightward gain: P = 0.003; reverse gain: P = 0.007; forward gain: P = 0.014) was significantly different across the diagnostic groups. Post hoc analyses showed that the control group required smaller leftward gain than spastic cerebral palsy, multiple sclerosis and upper-limb spasticity groups and smaller gain in all other directions compared with spastic cerebral palsy. Gain may be a useful parameter in tuning by clinicians, and efforts aimed at gain customization may aid the development of commercially available tuning software packages.

Comparison of Virtual Wheelchair Driving Performance of People With Traumatic Brain Injury Using an Isometric and a Conventional Joystick

Mahajan H, Spaeth DM, Dicianno BE, Collins DM, Boninger ML, Cooper RA. Comparison of virtual wheelchair driving performance of people with traumatic brain injury using an isometric and a conventional joystick. Objective To compare wheelchair driving performance in a driving simulator using a conventional joystick and an isometric joystick. Design Randomized, cohort study. Setting A research facility based in a hospital or in an independent living center. Participants Participants (N=20; 12 men, 8 women; mean age ± SD, 30.62±10.91y) who were at least 1 year post-TBI. Interventions Driving performance using an isometric joystick compared with a conventional movement joystick. Main Outcome Measures Average trial completion time, and trajectory-specific measures measured orthogonal to the center of driving tasks: root mean squared error, movement offset, movement error, and number of significant changes in heading. Results After statistically controlling for driving speed, participants were able to complete the driving tasks faster with an isometric joystick than while using a conventional movement joystick. Compared with the conventional joystick, an isometric joystick used for driving forward demonstrated fewer driving errors. During reverse driving the conventional joystick performed better. Conclusions The customizable isometric joystick seems to be a promising interface for driving a powered wheelchair for individuals with TBI.

Development of a Wheelchair Virtual Driving Environment: Trials With Subjects With Traumatic Brain Injury

Spaeth DM, Mahajan H, Karmarkar A, Collins D, Cooper RA, Boninger ML. Development of a wheelchair virtual driving environment: trials with subjects with traumatic brain injury. Objective To develop and test a wheelchair virtual driving environment that can provide quantifiable measures of driving ability, offer driver training, and measure the performance of alternative controls. Design A virtual driving environment was developed. The wheelchair icon is displayed in a 2-dimensional, bird's eye view and has realistic steering and inertial properties. Eight subjects were recruited to test the virtual driving environment. They were clinically evaluated for range of motion, muscle strength, and visual field function. Driving capacity was assessed by a brief trial with an actual wheelchair. During virtual trials, subjects were seated in a stationary wheelchair; a standard motion sensing joystick (MSJ) was compared with an experimental isometric joystick by using a repeated-measures design. Setting Subjects made 2 laboratory visits. The first visit included clinical evaluation, tuning the isometric joystick, familiarization with virtual driving environment, and 4 driving tasks. The second visit included 40 trials with each joystick. Participants Subjects (n=8; 7 men, 1 woman) with a mean age of 22.65±2y and traumatic brain injury, both ambulatory and nonambulatory, were recruited. Interventions The MSJ used factory settings. A tuning program customized the isometric joystick transfer functions during visit 1. During the second visit, subjects performed 40 trials with each joystick. Main Outcome Measure The root mean square error (RMSE) was defined as the average deviation from track centerline (in meters) and speed (in m/s). Results Data analysis from the first 8 subjects showed no statistically significant differences between joysticks. RMSE averaged .12 to .21m; speed averaged .75m/s. For all tasks and joysticks, driving in reverse resulted in a higher RMSE and more virtual collisions than forward driving. RMSE rates were greater in left and right turns than straight and docking tasks. Conclusions Testing with instrumented real wheelchairs can validate the virtual driving environment and assess whether virtual driving skills transfer to actual driving.

Isometric Force Production in Experienced Fighter Pilots During +3 G<SUB>z</SUB> Centrifuge Acceleration

Previously, we have shown that naïve subjects produce exaggerated isometric forces when exposed to increased acceleration (+Gz) for the first time. The present study investigates whether +G,-experienced PA-200 Tornado pilots show similar deficits. Experiments were conducted in the stationary (+1 Gz) or rotating (+3 Gz) gondola of a human-rated centrifuge. With their dominant hand, seven pilots produced visually prescribed forces of specific direction and magnitude using an isometric joystick. In practice trials, subjects received continuous visual feedback about their performance, while in test trials they did not. Peak forces during test trials were significantly higher in +3 Gz than in +1 Gz, although this increase of about 25% referring to the +1 Gz value was somewhat smaller in pilots than in nonpilot controls (increase of about 36%). Since pilots' responses were exaggerated in +3 Gz, it seems that frequent exposure to varying +Gz levels is not sufficient for a profound adaptation of force-producing mechanisms to +3 Gz. In consequence, pilots' performance on isometric tasks could be compromised during flight maneuvers in +Gz.

Acceleration Effects on Manual Performance With Isometric and Displacement Joysticks

We have shown before that novice human subjects produce exaggerated isometric forces when exposed to three times normal terrestrial acceleration (+3 Gz), and that this deficit is compensated by intensive training in +3 Gz. We now investigate whether training in normal terrestrial gravity (normal G) is also effective. We further examine whether subjects in +3 Gz produce not only exaggerated forces, but also exaggerated hand displacements. Experiments were conducted in the stationary (normal G) or rotating (+3 Gz) gondola of a man-rated centrifuge. With their dominant hand, subjects produced either forces using an isometric joystick, or hand displacements using a regular joystick. Response directions and magnitudes were prescribed visually. In practice trials, subjects received continuous visual feedback about their performance, while in test trials they did not. Subjects produced exaggerated forces in +3 Gz, whether or not they previously practiced the task in normal G. In contrast, subjects did not produce exaggerated hand displacements in +3 Gz. Exaggerated force production in +3 Gz is not overcome by task practice in normal G, as opposed to task practice in +3 Gz. This might be an indication that pilot training should contain extended practice of force production during phases of increased gravity (+Gz) to avoid motor deficits during flight maneuvers inducing +Gz. Furthermore, the control of isometric and regular joysticks seems to be based on partly distinct neural mechanisms, with different +Gz dependence. Thus, against the background of motor performance during +Gz, regular sticks might be favorably compared to isometric sticks in high-performance aircrafts.

Force Control Strategies While Driving Electric Powered Wheelchairs With Isometric and Movement-Sensing Joysticks

Innovations to control interfaces for electric powered wheelchairs (EPWs) could benefit 220000 current users and over 125000 individuals who desire mobility but cannot use a conventional motion sensing joystick (MSJ). We developed a digital isometric joystick (IJ) with sophisticated signal processing and two control functions. In a prior study, subjects' driving accuracy with our IJ was comparable to using an MSJ. However, we observed subjects using excessive force on the IJ possibly because its rigid post provides no positional feedback. Thus, this paper examines the time-series data recorded in the previous study to characterize subjects' force control strategies since weakness is a concern. Eleven EPW users with upper limb impairments drove an EPW using an IJ with two different control functions and an MSJ in a Fitts' law paradigm. Subjects relied upon positional feedback from the MSJ and used appropriate force. In contrast, subjects using the IJ with either control function applied significantly higher force than necessary (p < 0.0001 and p = 0.0058). Using higher average force was correlated with quicker trial times but not associated with accuracy. Lack of positional feedback may result in use of excess isometric force. Modifying control functions, adjusting gain, or providing additional training or feedback might address this problem.

Advancements in Power Wheelchair Joystick Technology: Effects of Isometric Joysticks and Signal Conditioning on Driving Performance

An estimated 125,000 Americans with movement disorders that preclude independent mobility in a power wheelchair could benefit from improved control devices. We developed variable gain algorithm (VGA) software for our isometric joystick (IJ) that allows it to emulate a commercially available motion-sensing joystick (MSJ) in performance but retain the unique customizable features of an isometric control. Force sensing algorithm (FSA) software allowed the IJ to function as a simple isometric device. Using a Fitts' Law paradigm, we compared driving performance with floor targets using a standard MSJ and an IJ with both FSA and VGA software in 11 electric power wheelchair users with a variety of impairments. Outcome measures were reaction time (RT), movement time (MT), and driving accuracy (DA). The IJ with FSA had a significantly shorter RT than the MSJ (P < 0.0020). The IJ with FSA had a significantly longer MT than the MSJ to far targets (P < 0.0159). No differences were found between the IJ with VGA and the MSJ with respect to RT or MT. No differences in DA were found among any of the joysticks. VGA software allowed the IJ to function similarly to the MSJ with respect to RT, MT, and DA.

Comparison of virtual and real electric powered wheelchair driving using a position sensing joystick and an isometric joystick

There are limited interface options for electric powered wheelchairs, which results in the inability of some individuals to drive independently. In addition, the development of new interface technologies will necessitate the development of alternative training methods. This study compares a conventional position sensing joystick to a novel isometric joystick during a driving task in a virtual environment and a real environment. The results revealed that there were few differences in task completion time and root-mean-square error (RMSE) between the two types of joysticks. There were significant correlations between the RMSE in the virtual environment and the real environment for both types of joysticks. The data indicate that performance in the virtual environment was representative of driving ability in the real environment, and the isometric joystick performed comparably to the position sensing joystick.

Analysis of position and isometric joysticks for powered wheelchair driving.

The control interface is one of the most critical components of the electric-powered wheelchair (EPW). The control interface must accommodate the user's limitations and maximize the user's abilities. This study extended Fitts' Law for target-acquisition to a continuously updated target. The extended Fitts' Law was used to examine EPW driving with a standard position sensing joystick and a prototype isometric joystick (IJ). The extended Fitts' Law provides insight into the difficulty of performing target-acquisition tasks with an EPW. The test results showed significant differences (p < 0.05) among the two types of joysticks for selected measures of information processing capacity, movement time, root-mean-square-error, and average velocity while performing turning maneuvers. The mean values indicate that the IJ may provide superior turning performance.

Force sensing control for electric powered wheelchairs

People with many types of disabilities use electric powered wheelchairs (EPWs) for mobility. Excessive intention tremor, limited range of motion, athetoid motions, and spastic rigidity can reduce or prohibit the control over an EPW. This study focused on the design and testing of a newly developed isometric joystick (IJ) for EPW control. The IJ was tested against existing performance standards and compared to a commercial position sensing joystick (PSJ). When averaged across all subjects (both controls and impaired subjects) the root-mean-square tracking error and time to complete the driving course were not significantly different when using the rule (p<0.05). Results within a subject, however, did show significance. Across all subjects, nevertheless, the IJ was superior to the PSJ for two tasks: driving straight and driving in a circle. Further development of control algorithms, especially the implementation of digital control, could lead to greater improvement in performance with the IJ.

Performance of children with cerebral palsy with an isometric joystick

Performance of children with cerebral palsy with an isometric joystick

Visually controlled matching of pattern movement.

Subjects were asked to match the speeds of two moving random-dot patterns seen through circular apertures. The speed of one pattern that moved horizontally toward the right of a computer screen changed continuously. The speed of this pattern represented the target. It was to be matched with the speed of the second pattern, which moved in the opposite direction. The subject controlled the speed of the second pattern by means of an isometric joystick. The distance between the apertures on the screen as well as the subject's distance from the screen served as experimental parameters. In this way, the effects of both spatial and temporal transients of pattern speed on human tracking performance were studied. To avoid anticipation by the subject, the amplitude and the frequency of the target pattern speed changed pseudorandomly. The accuracy with which the subject performed the matching task was influenced by the mean pattern speed and the parameters of the visual field. Within lower velocity ranges, the subject's sensitivity to the instantaneous speed differences varied according to Weber's law. The cross-correlation of the velocity time courses decreased when the mean speed of the target pattern was increased. Two stimulus parameters had a strong influence on the modulation of the correlation value: (1) the angular size of the stimulus on the retina and (2) the retinal eccentricity of the stimulus.

Isometric Joystick: A Study of Control by Adolescents and Young Adults with Cerebral Palsy

This research was undertaken to determine the best wheelchair driving method for clients with cerebral palsy who were experiencing difficulties using displacement joysticks. The hypothesis was that adolescents with cerebral palsy would perform better in a tracking task using an isometric joystick (which has no moving parts) than a displacement joystick of the type used in commercial wheelchair controllers. A series of single subject case studies was performed in which the activating force of the isometric joystick was individualised for each subject. Comparative evaluation of the isometric joystick and a displacement joystick was then carried out. Results indicate that performance using the displacement joystick was superior to performance with the isometric joystick for the able-bodied subject and four of the five subjects with cerebral palsy. One of the subjects showed significantly better performance on the displacement joystick using his hand, and no significant difference between joysticks using his foot. The remaining subject, who used his foot, showed no significant difference between joysticks. These findings suggest that subjects with cerebral palsy with prior experience using a displacement joystick do not appear to benefit by the use of an isometric joystick compared to a displacement joystick. No difference in the use of the two joysticks was found for subjects with cerebral palsy who had no prior experience using a joystick. This suggests that an isometric joystick is an option for people beginning to learn to drive an electric wheelchair.

Using Velocity Control to Navigate 3D Graphical Environments: A Comarison of three Interfaces

Three velocity control interfaces to three dimensional virtual environments are compared. The interface devices are: a six degree of freedom position sensor, a six degree of freedom isometric joystick, and a conventional mouse in conjunction with a soft control panel displayed on the monitor. In each interface the devices are used to control velocity, and all make use of a quadratic function to map the input to the viewpoint velocity. We use two structured exploration tasks to assess the usability of the different interfaces. In the first task an interviewing technique is used in conjunction with an exploration task which involved examining widely spaced details of the 3D scene. The second task is designed to reveal how well users can interact at different scales using the different devices. Subjects are required to navigate through a tube which varies over four orders of magnitude in size. The results show that subject's behavior is highly constrained by the local size of the tube: they maintained a constant velocity relative to the local size of the tube. They also showed differences in the effectiveness of the different devices in determining traversal rate that the positioning device and the control panel were about equally effective for fast navigation, and both are better than the isometric joystick.

Control Systems Analysis of Computer Pointing Devices

A theoretical framework for the ergonomic evaluation of manual pointing devices is discussed. Pursuit tracking is suggested as an alternative to the conventional “target acquisition” approach to evaluating pointer performance. Subjects' ability to control the position of a pointer on a CRT display was evaluated in a series of two-dimensional pursuit tracking tasks in which the frequency of target movement was varied. Performance was compared under identical conditions using a mouse and an isometric joystick. Quality of control was measured by RMS error and stability of the controlled variable. The mouse allowed better control of pointer position. The superiority of the mouse was most evident with low-frequency target movements. The results indicate the importance of evaluating pointing devices under user-friendly conditions.

A microprocessor environmental controller for quadriplegics

An environmental controller has been designed using consumer available components. Its flexibility, versatility, and reduced cost, are a direct result of using an isometric joystick, a microprocessor and software package in a configuration that lends itself very readily to change.