GB2159111A - Driver assessment system - Google Patents

Abstract

A system for assessing a person's capability to perform one or more driving functions comprises a force-sensing steering wheel (11) for fitment on a steering column of a motor vehicle or a vehicle simulator and having a sensor, for example a strain gauge arrangement, responsive to rotational forces applied to the steering wheel, and an analysing/display unit (10) providing an indication of such forces for comparison with base-line measurements. The system may further include a brake pedal force sensor (14) for measuring user-applied forces and a timing arrangement operable in conjunction with the brake pedal force sensor for measuring a person's reaction times in, for example, emergency stop situations. <IMAGE>

Description

SPECIFICATION Driver assessment system System for Assessing Driving Capabilities This invention relates to systems for assessing a person's driving capabilities, and is particularly concerned with systems for assessing the capabilities of a person physically to perform one or more functions necessary to drive a motor vehicle.

The invention is intended especially for use in assessing the ability of disabled or handicapped persons to perform vehicle driving functions. Nowadays, many ordinary production road vehicles are readily capable of modification or adaptation, to some extent at least, to meet the individual requirements of a disabled person whereby the vehicle can be driven in a safe manner by the person concerned.

Considering, for example, the case of disabled persons whose disabilities impose limitations on their physical strength, a production road vehicle may conveniently be adapted by the provision of power assistance to such a driving function as steering. Of course, power- assisted steering systems are already commonly available in many production vehicles as original equipment but their operational characteristics are, naturally, chosen to suit drivers whose physical strength is around the normal average.It may be that the degree of power assistance needed by a disabled person to control the steering function satisfactorily is greater than that afforded by an original equipment power-assisted steering system in which case it may be necessary to modify the system to meet the particular demands of the individual disabled person, by perhaps changing the operational characteristics of the system to provide for example a variable amount of power assistance, and also by revising the lay-out or configuration of the user-operable controls for ergonomic reasons to meet the person's limitations.

Disabilities affecting limb mobility, e g. the ability to move arms freely to control a steering wheel, need also to be considered.

There exists a need therefore to be able to determine, firstly, whether a person's disabilities are of such a nature that they can be accommodated by suitable modification of the vehicle, and, secondly, the form of the modification and the performance characteristics of the equipment necessary for conversion of the vehicle to meet the individual's requirements. Heretofore, the assessment of a person's ability to drive and the extent and nature of any necessary modifications has commonly been the responsibility of assessors experienced in this field who carry out this duty using their personal skills and judgement. However, assessment in this manner is not an easy task.For example, taking the steering function, difficulties can be experienced in determining the optimum amount of power-assistance required whilst at the same time retaining within the steering system a degree of "feel" for the benefit of the driver. The assessment of a person's driving abilities in this way may not therefore always be entirely satisfactory.

It is an object of the present invention to provide a system which enables a person's physical capabilities for performing a driving function to be determined conveniently, and in particular the function of steering a motor vehicle.

According to the present invention, there is provided a system for assessing the capability of a person to perform a driving function comprising a steering wheel adapted to be mounted on a steering column of a vehicle or a vehicle-simulator, the steering wheel having sensing means associated therewith for sensing the extent of force applied thereto in use by a person operating the steering wheel and generating a signal which varies in accordance with that force, and analysing means for receiving the signal generated by the sensing means and providing an indication of the extent of that force.

The system may be employed in a standard motor vehicle or, alternatively, in a vehicle simulator, for example, a static test rig which simulates the characteristics of a motor vehicle as regards the steering function and possibly other driving functions.

The steering wheel of the system may comprise a first part providing a user-engagable portion, for example a conventional rim, through which a user can rotate the steering wheel around its axis, a second part adapted to be coupled to a steering column and connected to the first part so as to permit deflection of the first relative to the second part upon rotational force being applied to the first part in use, the extent of which relative deflection varies in accordance with the amount of rotational force applied to the first part by a person being assessed. In such an arrangement, the sensing means may conveniently be arranged to sense the extent of the aforementioned relative deflection between the two parts in use and generate a signal in accordance therewith.

The first and second parts may be interconnected by resiliently flexible means, for example a flexure member attached to one of the parts and engaging with a portion of the other, through which rotational movement of the first part is transmitted to the second part, and which, in use, is flexed in response to rotational force applied to the first part.

The sensing means may comprise one or more strain gauges carried by the means interconnecting the first and second parts so as to sense flexing of that means.

In addition to assessing the person's ability to perform the steering function for driving a vehicle, it is also desirable to be able to assess the person's ability to perform the braking function, i e.

operation of the brake pedal. For this reason, the system may further include a second sensor, for example a load cell, adapted to be connected to the brake pedal in a motor vehicle or vehicle simulator, and preferably between the brake pedal and floor pan of the vehicle or simulator, for sensing the amount of force applied to the brake pedal by a person being assessed and generating signal in accordance therewith, the sensor being connected with the analysing means to provide an indication of that force. The sensor may itself provide resistance to deflection of the brake pedal, this resistance increasing in proportion to the extent of deflection.

Furthermore, the analysing means may include a timing arrangement for assessing reaction times of a person, that is, the time taken by a person being assessed to respond to a given stimulus and perform a driving function. In such a case, the timing arrangement preferably comprises initiating means operable to provide a start signal, for example a visual light signal, to a person being assessed and simultaneously to initiate operation of a timer, and terminating means for terminating operation of the timer in response to a signal received from the brake pedal sensor indicative of a predetermined brake pedal force having been achieved. Operation of the initiating means may be controlled by means of a remote control device.

A system for assessing the physical capabilities of a person to perform driving functions in accordance with the present invention, and for use either in a motor vehicle or a vehicle simulator, will now be described by way of example, with reference to the accompanying drawings in which: Figure 1 is a schematic view of the system which provides for the assessment of steering, braking and reaction time performance of a person being assessed; Figure 2 is a part cross-section view of a steering wheel of the system of Figure 1 through two planes intersecting along the wheel axis X-X; and Figure 3 shows a brake pedal pressure sensor employed in the system of Figure 1.

Referring to Figure 1, the assessing system comprises an electronic analysing and display unit 10, a steering wheel 11 having a sensor for providing through a lead 12 an electrical signal to the unit 10 in accordance with the amount of rotational force applied thereto in use by a person being assessed, a brake pedal force sensor 14 for providing through a lead 15 an electrical signal to the unit 10 indictive of the amount of force or load applied to a brake pedal 16 by the person being assessed.

The embodiment of the system shown further includes a remote control device 17 connected to the unit 10 through a lead 18 for initiating operation of a a timing arrangement within the unit 10, and a signal lamp unit 19, associated with the timing arrangement, connected to the unit 10 through a lead for positioning remotely from the unit 10 in the field of view of the person being assessed. The unit 10 contains standard electronic circuitry for suitably amplifying and conditioning the electrical signals obtained from the steering wheel and brake pedal force sensors and includes on its front panel output displays, for example liquid crystal displays, 20 and 21 for providing digital representations in accordance with the values of these electrical signals from the steering wheel and brake pedal force sensors respectively.The unit's electronic circuitry in this respect may be of conventional form and thus will not be described in detail.

A further digital display, 22, is provided by the unit 10 for displaying a person 5 response time, as will be described later, determined by a timing circuit, again of conventional form, also contained within the unit 10.

Each of the respective circuits within the unit 10 associated with the displays 20 and 21 has provision for adjustment and selection, there being provided on the front face of the unit 10 zeroising and calibration ("span") adjustment controls, for example 24 and 25, a shared calibration mode switch 26, and a selection switch 27 for selecting either a normal readout of the respective sensor signal value or a peak hold facility. A reset switch 28 is also provided for resetting the displays when in the latter mode.

The electronic circuitry within the unit 10 associated with the reaction timer display 22 includes a SET switch 29 which, when operated, permits a desired predetermined brake pedal load force required, as will be described, to terminate operation of the timer during response time measuring mode of operation of the system to be entered by means of the adjustment control 30 and its value displayed by display 22.

The unit 10 is conveniently powered by internal batteries so that it is easily transportable between vehicles and or simulators. The batteries also supply power to the steering wheel and brake pedal sensors as required. A low-battery level warning light is provided in conjunction with a 'power-on' light associated with a main power switch on the front face of unit 10 to indicate low battery reserves. Of course, the unit 10, when used in a vehicle, may alternatively be powered by the vehicle's electrical system, for example through the vehicle's cigar-lighter socket.

Referrinq now to Figure 2, there is shown a partsectional view of the steering wheel 11 of the assessment system taken through two planes which are parallel to, and intersect one another along the central vertical axis X-X of the steering wheel. The steering wheel 11 is shown connected to a conventional steering column 40 provided in a motor vehicle or vehicle simulator in the normal manner. In this respect, a lower, generally cylindrical, hub part 41 of the steering wheel has an inner centrally disposed, concentric tubular portion 42 which is fitted over the splined end of the steering colum 40 and secured thereon by means of clamping washers and a nut engaging with the screw-threaded outermost end section of the steering column.

The hub part 41 defines an outer cylindrical wall 43 extending co-axially with the steering column 40 which has an outwardly directed flange at the upper end thereof upon which a generally circular plate 45 extending radially inwards is immovable mounted by means of screws 44, only one of which is visible in Figure 2. Extending through a central aperture in the plate 45, and securely attached thereto by bolts 46 passing through respective overlapping shoulders, is a support member 47. The support member 47 carries a further generally circular plate 48 which is mounted for rotational movement thereon by a bearing 49 disposed between respective cooperating circular shoulders on the member 47 and plate 48. The plate 48 is of similar diameter to the plate 45 and lies parallel with the plate 45 transversely of the steering wheel axis.A bolt member 50 having an enlarged head 51 passes through a central aperture in the plate 48, with a circular radially-extending shoulder on its enlarged head overlying a correspondingly directed shoulder defined by the central aperture of the plate 48, and through a central bore of the support member 47 axially aligned with the steering column 40. A nut 52 on the screw threaded end of the bolt member 50 engages with the underside of support member 47, remote from the plate 48, so as to retain rotatably the plate 48 on the support member 47 via the bearing 49. A thrust washer 53 is disposed between the aforementioned cooperating radially-extending shoulders of the bolt member 50 and the circular plate 48 so as to permit the plate 48 freely to rotate about the axis of the steering wheel with respect to the support member 47, and thus the circular plate 45 and hub part 41.

A circular boss 54 formed integrally with radiating spokes 55 that carry a manually grippable, conventional rim of the steering wheel (not shown) is secured to the plate 48 via bolts (also not visible in figure 2). Disposed between the boss 54 and the plate 48 is an inverted cup-shape shroud 56 covering the plate 48 and extending axially downwards to a position adjacent the outer edge of plate 45.

The plate 48, which, it will be understood, rotates together with the steering wheel rim, is mechanically coupled to the plate 45, in order to transmit rotational movements of the steering wheel rim to the hub part 41 and thus the steering column 40, by means of two flexure members 58 disposed at diametrically opposite positions around the axis of the steering wheel and connecting respective peripheral portions of the plates 45 and 48. More precisely, the flexure members 58, only one of which is visible in Figure 2, are secured by bolts 59 at their one end in respective cut-outs 60 in the periphery of the plate 45 and project upwardly such that their other ends engage in vertically aligned cut-outs 61 in the periphery of the plate 48.

Thus, rotational displacement of the steering wheel rim is transmitted by plate 48 to plate 45, and hence column 40, via the flexure members 58.

The flexure members 58, formed of resilient steel or the like, are relatively stiff but are designed to flex slightly in response to rotation of plate 48, the amount of flexing being dependent on the resistance to turning of the steering column 40 afforded by the vehicles steering system, or in the case of a simulator, an artificially created resistance, and the amount of force, i.e. torque applied by a user to the steering wheel rim in overcoming that resistance. In order to sense this deflection, and provide an indication of the amount of torque applied, a respective wire strain gauge is incorporated in each of the flexure members 58 to generate, when connected to the unit 10, an electrical signal which varies in accordance with the amount of deflection, and thus torque.Electrical connection with the strain gauges is made via a DIN socket 62 mounted in a peripheral aperture in the plate 48 by a mating DIN plug attached to the lead 12.

Mechanical stops are provided (not shown) to limit the extent of relative displacement between the plates 45 and 48.

The strain gauges convert steering effort, i.e.

torque, applied to the wheel rim into electrical signals and, together with circuitry within the unit 10, form part of an electrical bridge circuit configuration. Having suitably calibrated the unit 10 beforehand, the amount of steering effort or torque applied to the steering wheel by a person under assessment can be read directly from the display 20. Such readings could be taken, in the case of a road vehicle, either whilst the vehicle is stationary, the natural resistance to steering whilst in this condition perhaps supplemented by additional restraint against road wheel movement depending on the circumstances, providing the necessary resistance to turning of the steering column, or alternatively whilst the vehicle is being driven along the road.In each case, a person's performance in applying force to the steering wheel can be measured and particularly during certain routines such as the execution of left and right hand turns and "hand over the top" movements. Similar tests may be made in a simulator where artificial resistance is imposed on the steering column or where rotational force is deliberately applied to the steering column by suitable means to assess a person's ability to resist turning.

Measurements taken from the unit 10 are then compared with "base line" measurements taken from a variety of persons having average physical capability. Hence, a person's ability to perform the steering function, and more especially their limitations as regards torque applying effort and limb mobility, can be readily assessed using the system and a suitable power assistance system tailored to meet individual requirements accordingly. The steering wheel could of course also be used for normal driving of a road vehicle if desired simply by unplugging the lead 12 so as to permit unhindered rotation of the steering wheel.

It will be appreciated that the number of flexure members 58 and strain gauges employed can be varied as desired.

Referring now to Figure 3, the brake pedal force sensor 14 is designed to be fitted between the brake pedal and floor pan of the motor vehicle, or vehicle simulator, as the case may be. The sensor 14 includes a main body 70, in which is housed a load cell, comprising a flexure member (not visible) incorporating a strain gauge coupled between the body 70 and one end of a support arrangement 71 telescopically received within the body 70. A pivot roller 72 is mounted at the upper end of the body 70 and engages with the underside of the foot rest of the brake pedal 16 such that the components of movement of the brake pedal 16 other than substantially vertical one accommodated by rolling of the pivot roller 72 across the underside of the pedal.The sensor 14 is secured to the brake pedal by means of a strap 74 passed around the pedal and pivotally attached to the axle of the pivot roller 72.

The support arrangement 71 is pivotally connected at its end 75 remote from the body 70 to a non-slip pad 75 and is adjustable in axial length by an adjustment wheel 77 so that the sensor is adaptable to suit a variety of spacing between brake pedal and floor, and angle of floor.

The lead 15 passes through the body 70 and is connected to the strain gauge contained therein.

In operation, depression of the brake pedal, either by a user's foot or perhaps manually through a linkage if necessary, causes deflection of the load cell of the sensor and a corresponding output from the electrical strain gauge. The signal from the strain guages varies in accordance with the extent of depression of the brake pedal and thus in accordance with force or load applied by a user to the brake pedal. Resistance to brake pedal movement is provided by the flexure member and the amount of its deflection will thus depend on the force applied. Some resistance will also be provided by the vehicle's brake system, and this would normally be taken into account when assessing measurements. The output from the sensor 14 is conditioned and displayed by the unit 10, on display 21, having been suitably calibrated beforehand.The readings can be compared with baseline information and a person's limitations in force application to the vehicle's brake pedal, and their ability to perform the braking function, can be assessed accordingly. Appropriate power assistance can then be tailored to suit their needs, if possible.

Referring now again to Figure 1, the assessing system, as previously mentioned, includes a response time assessment capability. More particularly, the system is arranged to permit measurement of a person's reaction time to an emergency stop situation. The system accomplishes this in the following way.

The signal lamp unit 19 is positioned in front of the person being assessed, preferably on the vehicle's dashboard, and the remote control unit 17 located out of the field of view of that person so that any forewarning of the initiation of a test procedure is avoided. It is assumed that the unit 10 has suitably been programmed beforehand with a preselected value of brake pedal force sensor reading having been entered and stored in a memory.

The person under assessment is required to operate the accelerator pedal at full depression. To initiate a test sequence, a "start" switch on the remote control unit 17 is operated whereupon the signal lamp of unit 19 is immediately illuminated and the electronic timer within the unit 10 simultaneously activated to commence counting up in tenths of a second, the elapsed time being continuously displayed on display 22. The person under assessment is required, as would be the case in a typical normal emergency top situation, to transfer his foot to the brake pedal and achieve the preset pedal force as quickly as possible upon seeing the illuminated lamp.A comparison circuit withing the unit 10 continually compares the actual brake pedal force with the preselected level of force and as soon as the preselected level of brake pedal force is attained, operation of the timer is automatically terminated within the unit 10 and the time elapsed till that point held by the display 22.

Again, as with the assessment of ability to perform driving functions described previously, the response time measurement or series of measurements, is compared with "base line" information, and assessment can be made of a person's reaction time and their ability to respond to an emergency stop situation.

Following the completion of a response time measuring sequence, the unit 10 can be reset by operation of a further switch on the remote control unit 17 so that a further sequence may then be initiated.

Measurements by the unit 10 of steering force, brake pedal force and response times may be fed through an output lead 80 to a remote electronic data storage unit for later analysation or to a remote printer from which a hard copy print-out can be obtained.

Claims (14)

1. A system for assessing the capability of a person to perform a driving function comprising a steering wheel adapted to be mounted on a steering column of a vehicle or a vehicle-simulator, the steering wheel having sensing means associated therewith for sensing the extent of force applied thereto in use by a person operating the steering wheel and generating a signal which varies in accordance with that force, and analysing means for receiving the signal generated by the sensing means and providing an indication of the extent of that force.

2. A system according to Claim 1, wherein the steering wheel comprises a first part providing a user-engagable portion through which a user can rotate the steering wheel around its axis, a second part adapted to be coupled to a steering column and connected to the first part so as to permit deflection of the first part relative to the second part upon rotational force being applied to the first part in use, the extent of which relative deflection varies in accordance with the amount of rotational force applied to the first part by a person being assessed.

3. A system according to Claim 2, wherein the sensing means is arranged to sense the extent of said relative deflection between the two parts and generate a signal in accordance therewith.

4. A system according to Claim 2 or Claim 3, wherein the first and second parts are interconnected by resiliently flexible means through which rotational movement of the first part is transmitted to the second part, and which, in use, is flexed in response to rotational force applied to the first part.

5. A system according to Claim 4, wherein the resiliently flexible means comprises a flexure member attached to one of the parts and engaging with a portion of the other part.

6. A system according to Claim 4 or Claim 5, wherein the sensing means comprises one or more strain gauges carried by said means interconnecting the first and second parts so as to sense flexing of said means.

7. A system according to any one of the preceding claims, wherein the system includes means for assessing a person's ability to perform a braking function comprising further sensing means adapted to be connected to a brake pedal in a motor vehicle or vehicle simulator for sensing the amount of force applied to the brake pedal by a person being assessed and generating a signal in accordance therewith for supply to the analysing means.

8. A system according to Claim 7, wherein the further sensing means is adapted to be connected between the brake pedal and an immovable part of the motor vehicle or vehicle simulator so as to sense displacement of the brake pedal relative to said immovable part.

9. A system according to Claim 7 or Claim 8, wherein said further sensing means provides resistance to deflection of the brake pedal which increases in proportion to the extent of deflection.

10. A system according to any one of Claims 7 to 9, wherein said further sensing means comprises a load cell.

11. A system according to any one of the preceding claims, wherein the analysing means includes a timing arrangement for assessing a person's reaction times in performing a driving function in response to a given stimulus.

12. A system according to Claim 11 together with any one of Claims 7 to 10, wherein the timing arrangement comprises initiating means operable to provide a start signal to a person being assessed and simultaneously to initiate operation of a timer, and terminating means for terminating operation of the timer in response to a signal received from the further sensing means associated with the brake pedal indicative of a predetermined brake pedal force having been achieved.

13. A system according to Claim 12, wherein operation of the initiating means is controlled by means of a remote control device away from the person being assessed.

14. A system for assessing the capability of a person to perform a driving function substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.