GB2445291A

GB2445291A - Vehicle speed control

Info

Publication number: GB2445291A
Application number: GB0801412A
Authority: GB
Inventors: Karen Bishop
Original assignee: CONNAUGHT ENGINNEERING Ltd
Current assignee: CONNAUGHT ENGINNEERING Ltd
Priority date: 2004-08-18
Filing date: 2004-08-18
Publication date: 2008-07-02
Anticipated expiration: 2024-08-18
Also published as: GB2417335B; GB2417335A; GB0418437D0; GB2445291B; GB0801412D0

Abstract

A system for limiting the speed of a vehicle having an accelerator control whereby a driver of the vehicle can vary the speed of the vehicle, the system comprising: a limiter for preventing the speed of the vehicle from exceeding a limit speed; and limit speed setting means operable during operation of the vehicle to set the limit speed, whereby while the limiter is activated, the driver is prevented from increasing the speed above the said limit speed, and an accelerator sensor for sensing the position of an accelerator control wherein the limiter is deactivated when the accelerator sensor senses that the accelerator control is outside a preset threshold.

Description

VEHICLE SPEED CONTROL

This invention relates to controlling the speed of a vehicle, for example a motor vehicle.

In normal driving the driver of a motor vehicle can directly control the speed of the vehicle by varying the power output of the engine, for example by means of a throttle control such as an accelerator pedal. In addition, many motor vehicles are fitted with cruise control systems. These allow the driver to fix the speed of the vehicle at a specified value. Typically, when a vehicle's cruise control is activated the vehicle will be held at a set speed. The set speed is normally the speed at which the vehicle was travelling when the cruise control was activated, although some vehicles allow the set speed to be indexed up or down or allow a set speed to be stored and recalled later. With the cruise control activated the vehicle will maintain the set speed even if the driver releases the throttle control. To achieve this the vehicle automatically adjusts the power output of the engine in order to maintain the set speed. If the driver activates the throttle control to a setting beyond that selected by the cruise control system then the vehicle will travel faster than the set speed. If the driver activates the vehicle's brakes then the cruise control system will be deactivated and the vehicle will slow down.

Thus, the effect of a conventional cruise control system is to maintain a vehicle at a set speed, ignoring any setting of the throttle controller by the driver that corresponds to a speed lower than the set speed. And any setting of the throttle control that corresponds to a speed higher than the set speed will typically not deactivate the cruise control.

When a vehicle is being driven without the use of cruise control the driver must frequently check the speedometer in order to ensure that the vehicle is not exceeding the speed limit. This reduces the amount of attention that the driver can pay to the road conditions. As enforcement of speed limits increases drivers tend to pay increasing attention to the speedometer.

Drivers of vehicles that are equipped with cruise control can activate the cruise control to hold the vehicle's speed at a set speed that is below the speed limit.

This allows them more time to pay attention to the road conditions, and gives them confidence that they are not committing a traffic offence. However, when the vehicle approaches a hazard the driver should slow down to an appropriate speed, and if the driver has activated the cruise control he would have to deactivate it in order to slow down, usually by pressing the brake pedal, and subsequently reactivate the cruise control. Since this is inconvenient, the driver might choose to maintain the set speed through the hazard, which could be unsafe.

Some vehicles are fitted with a speed limiter that -for safety reasons -limits the vehicle's maximum speed and cannot be overridden or disabled by the driver.

There is a need for an improved means of speed control for vehicles.

According to one aspect of the present invention there is provided a system for limiting the speed of a vehicle having an accelerator control whereby a driver of the vehicle can vary the speed of the vehicle, the system comprising: a limiter for preventing the speed of the vehicle from exceeding a limit speed; and limit speed setting means operable during operation of the vehicle to set the limit speed; whereby, while the limiter is activated, the driver is prevented from increasing the speed above the said limit speed, and further comprising an accelerator sensor for sensing the position of the accelerator control, wherein the limiter is deactivated when the accelerator sensor senses that the accelerator control is outside a pre-set threshold.

The present invention will now be described by way of example with reference to the accompanying drawing. In the accompanying drawing: figure 1 is a schematic diagram of a motor vehicle; and figure 2 is a flow diagram illustrating the operation of a speed control system.

The vehicle 1 of figure 1 comprises an engine 2 for driving the wheels 3. The power output of the engine is dependent on factors including the setting of a control system 4, which regulates the power output of the engine. The setting of the control system is controlled by an engine management system 5 by means of a program stored in the engine management system operating in accordance with inputs received by the engine management system. The program is stored in a non-volatile memory 6 and executed by a processor 7. The inputs received by the engine management system are derived from sources that include: a speed sensor 8 for sensing the road speed of the vehicle, an accelerator sensor 9 for sensing the setting of accelerator pedal 10, switches 11-13 which are associated with a speed control system, and a brake sensor 14 which senses the position of brake pedal 15.

Whilst this embodiment is described with reference to an electronic engine management system, this is not essential. For example, mechanical speed control systems are known.

In a normal mode of operation of the vehicle the speed control system is not activated. The engine management system operates in the normal manner: i.e. without intervention from any cruise or speed control system. The power output of the engine is governed by the setting of accelerator pedal 10.

The operation of the speed control system will now be described. A driver of the vehicle operates the speed control system by means of switches 1 1-13 which provide inputs to the processor 7. The switches 11-13 have the following functions: switch 11 -activate speed control system switch 12 -deactivate speed control system switch 13 -unit selection for speed control system When the vehicle is being driven the driver can activate the speed control system by pressing switch 11.

Switch 13 allows the units in which the system operates to be selected: for example by selecting between miles per hour and kilometres per hour.

The processor allows a suitable limit speed to be selected automatically based on the speed of the vehicle when the system is activated and optionally whether the vehicle is accelerating or decelerating. This may be done in two general ways.

First, the processor could select as the limit speed the speed that is a whole multiple of 10 of the currently selected units and is either equal to the current speed or is the highest such speed that is lower than the current speed. Thus if miles per hour had been selected as the units and the current speed were from 30 to 39 mph then the limit speed would be set to 30 mph. In a variant of this method the processor could select as the limit speed the closest speed that is a whole multiple of 10 of the currently selected units to the current speed. In another variant of this method the processor could: i. if the vehicle is decelerating when the system is activated select as the limit speed the speed that is a whole multiple of 10 of the currently selected units and is either equal to the current speed or is the highest such speed that is lower than the current speed; or ii. if the vehicle is accelerating when the system is activated select as the limit speed the speed that is a whole multiple of 10 of the currently selected units and is either equal to the current speed or is the lowest such speed that is higher than the current speed.

Alternatively the processor could store a list of speeds corresponding to common speed limits in miles per hour and kilometres per hour, for example: 20 mph, 30 mph, 40 mph, 50 mph, 60 mph, 70 mph, 40 km/h, 50 km/h, 80 km/h, 100 km/h, km/h. When the system is operating in miles per hour only the stored speed limits in miles per hour would be used. When the system is operating in kilometres per hour only the stored speed limits in kilometres per hour would be used. When switch 11 is pressed the processor would identify the highest one of the speeds in the stored list that has the currently selected units and is less than or equal to the current road speed. This would be adopted as a limit speed.

The processor then controls the speed of the vehicle so as not to exceed the limit speed until the speed limitation is cancelled. Whilst the speed limitation is active, if the speed of the vehicle is exceeding the limit speed then the processor ignores the setting of the accelerator pedal and allows the vehicle to coast with little or no power being applied by the engine so that it can decelerate to the limit speed. If the speed of the vehicle is below the limit speed then the processor controls power output of the engine in accordance with the accelerator setting, as in the normal mode of operation. As a result, the vehicle can be driven normally, with the restriction that its speed cannot be increased over the limit speed by pressing the accelerator.

Pressing the deactivation switch 12 also cancels the maintenance of the speed limit and returns the vehicle to normal operation.

The speed limitation may be cancelled in a number of ways. In a preferred mode of operation the speed limitation may be maintained only whilst the accelerator is held in a position that is roughly appropriate for the current speed; otherwise the speed limitation is cancelled. This mode will be described in more detail below.

In operation, when the driver approaches a speed limit sign on the road he slows to a speed between the speed indicated on the sign and the next highest stored limit speed. Typically this will be up to around 10-15% above the indicated speed limit. He then presses the activation switch 11, which activates the speed control system to hold the indicated limit speed. The vehicle automatically slows down to that speed and although the speed of the vehicle is still under the driver's control, by means of the accelerator, he cannot increase the speed over the limit speed whilst the speed limitation remains active. On leaving the speed limit he cancels the speed control system by pressing switch 12 or depressing the accelerator significantly, as described in more detail below. Thus the system can reassure the driver that he will not exceed the speed limit, freeing him to concentrate on other driving tasks, whilst allowing deceleration and acceleration up to the limit with impunity.

When the driver approaches a speed limitation with the vehicle under direct control of the accelerator and then activates the speed limitation the accelerator will normally be at approximately the appropriate setting for the limit speed that is selected. Then, in the preferred mode of operation, the speed limitation is maintained while the accelerator remains within a pre-set threshold from the accelerator setting that would cause the vehicle to drive at that limit speed if the speed limitation were not active,. When the accelerator is moved outside a threshold zone the limitation is cancelled. In this mode the driver can use the speed limiter to keep the vehicle's speed at no higher than the limit speed, but can readily cancel the limitation to speed up or slow down when necessary. The threshold zone is preferably defined so that if the accelerator is released the speed limitation is not cancelled, but if the accelerator is pressed beyond a limit point then the limitation is cancelled. That limit point could be defined as a certain extent of the accelerator's travel: for example the limit of its travel or 80% or 90% thorough its travel towards that limit. Optionally, cancellation of the speed limit in this way could occur only if the accelerator exceeds the threshold when the vehicle is travelling at the limit speed; that would allow the vehicle to accelerate strongly whilst below the limit.

When the speed control system is active, it may optionally be deactivated by the processor in response to the brake pedal 15 being pressed as detected by sensor 14. Alternatively, the processor could be configured so that the system remains active when the brake pedal is pressed; this would usefully leave the limit speed in place even when the driver stops, for example at traffic lights in a speed limit zone.

When the speed control system is active it may optionally be deactivated by the processor in response to the accelerator being pressed beyond a pre-set limit point -for example to its furthest point, or to a point beyond a pre-set threshold of the point that it would be at to maintain the limit speed, as described above. This would allow the vehicle to accelerate beyond the set limit in an emergency situation, or on leaving the speed limit zone.

The program run by the processor 7 is preferably arranged to cause a display to be provided to the driver to indicate when the speed control system is active. This may be done by an indicator light on the vehicle's dashboard that simply indicates that the system is in operation, or more preferably by indicating the current limit speed on the vehicle's speedometer. To achieve this the speedometer could have a series of indicator lights at the positions corresponding to the stored limit speeds, which could be illuminated under the control of the processor 7.

In the embodiments described above the limit speed is set by means of a control operable by the driver of the vehicle. The control is preferably a manually actuable control such as a switch, although it could be (for instance) voice actuable. Instead of or in addition to the limit speed being set by the driver it could be set in response to signals received from a source external to the vehicle.

Transponders by the roadside could transmit signals indicative of a speed limit, which could be received and interpreted by the speed control system so as to set the limit speed in accordance with the speed limit indicated by the signals.

Figure 2 illustrates the flow of processing in the operation of one example of the system.

The switches 11 to 13 are preferably located in a position that allows them to be accessed conveniently by the driver: for example on the steering wheel of the vehicle.

The system could allow the driver to program the speeds in the stored list, to allow the vehicle to be used readily in jurisdictions that apply unusual speed limits.

The vehicle is preferably a road-going vehicle. The vehicle could, for example, be a car, van, truck, bus or motorbike.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

1. A system for limiting the speed of a vehicle having an accelerator control whereby a driver of the vehicle can vary the speed of the vehicle, the system comprising: a limiter for preventing the speed of the vehicle from exceeding a limit speed; and limit speed setting means operable during operation of the vehicle to set the limit speed; whereby, while the limiter is activated, the driver is prevented from increasing the speed above the said limit speed, and further comprising an accelerator sensor for sensing the position of the accelerator control, wherein the limiter is deactivated when the accelerator sensor senses that the accelerator control is outside a pre-set threshold.

2. A system according to claim 1 further comprising a first switch enabling the driver to activate the system.

3. A system according to claim I or claim 2 further comprising a memory having stored therein a list of limit speeds.

4. A system according to claim 3, the system further comprising a speed sensor for sensing the speed of the vehicle, the limit speed setting means further comprising a limit speed selector, and the system being arranged to, on activation of the limiter by the driver: sense, by means of the speed sensor, a current speed of the vehicle; and select, by means of the limit speed selector, as the said limit speed the highest one of the speeds in the stored list that is less than or equal to the current speed.

5. A system according to claim 4 further comprising a second switch, wherein: the stored list comprises speeds corresponding to vehicle speeds in miles per hour and vehicle speeds in kilometres per hour; the second switch enables the driver to select one of miles per hour and kilometres per hour as an operational unit; and the step of selecting comprises selecting as the said limit speed as the highest one of the speeds in the stored list that has the selected operational unit and that is less than or equal to the current speed.

6. A system as claimed in claim I or 2, comprising a speed sensor for sensing the speed of the vehicle, the limit speed setting means further comprising a limit speed selector, and the system being arranged to, on activation of the limiter by the driver: sense, by means of the speed sensor, a current speed of the vehicle; and select, by means of the limit speed selector, as the said limit speed the highest speed that is a whole multiple of 10 of a currently selected operational speed unit and that is less than or equal to the current speed.

7. A system according to claim 6 further comprising a second switch that enables the driver to select one of miles per hour and kilometres per hour as the operational unit.

8. A system according to any preceding claim further comprising a brake sensor for sensing the position of a brake control of the vehicle, wherein the system is deactivated when the brake sensor senses an application of the brake control by the driver.

9. A system according to any of claims 1 to 7 further comprising a brake sensor for sensing the position of a brake control of the vehicle, wherein the system is not deactivated when the brake sensor senses an application of the brake control by the driver.

10. A system according to any preceding claim further comprising a third switch enabling the driver to deactivate the system.

11. A system according to any preceding claim further comprising a fourth switch enabling the driver to vary the limit speed.

12. A system according to claim 11 wherein the fourth switch enables the driver to select, as the limit speed, a speed from the stored list.

13. A system accordin9 to claim 11 or claim 12 wherein the fourth switch enables the driver to enter a speed to be used as the limit speed.

14. A system according to claim 1 wherein the pre-set threshold is exceeded when the accelerator deviates by more than a pre-set amount from the point that would cause the vehicle to travel at the limit speed if the speed limiter were inactive.

15. A system according to claim 1 wherein the pre-set threshold is exceeded when the accelerator reaches the furthest point to which it accelerator can travel.

16. A system according to any preceding claim further comprising a display arranged to indicate to the driver when the system is activated.

17. A system according to claim 16 wherein the display is further arranged to indicate to the driver the said limit speed.

18. A system according to any preceding claim wherein the limit speed varying means is operable in response to signals transmitted from a point external to the vehicle.

19. A system according to any preceding claim wherein while the limiter is activated the driver is enabled to vary the speed of the vehicle by means of the accelerator control.

20. A speed limitation system substantially as herein described with reference to the accompanying drawings.