GB2443018A

GB2443018A - Vehicle accelerometer

Info

Publication number: GB2443018A
Application number: GB0620545A
Authority: GB
Inventors: Daniel White
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-10-17
Filing date: 2006-10-17
Publication date: 2008-04-23
Also published as: GB0620545D0

Abstract

An accelerometer designed for use in vehicles, for the purpose of giving the users quantified information about the weight transfer between the vehicle's wheels. Preferably a mechanical device in which one or more weights (9) are able to slide, roll or pivot with the minimum of friction against one or more springs (15) and which may present information about the displacement of the spring(s) (15) to the users by way of a pointer against a dial scale. The weight(s) (9) should have dead stops at their resting positions to prevent them from conserving momentum. The unit may provide a self-levelling system in a gimbal mounting arrangement. It may also provide a high point marker (17, fig.14) to record the highest acceleration forces experienced.

Description

I

1 2443018

ACCELEROMETER

The invention relates to on accelerometer that communicates information about the nature of acceleration forces experienced by any road going vehicle to the driver and/or third party (e.g. examiner, driving instructor, passenger, vehicle owner).

Every operation that a driver performs when controlling a vehicle will produce an acceleration of some kind. Whether one is concerned with speed, efficiency, safety or comfort, the standard of driving can be assessed to some extent by analysing the acceleration forces experienced.

A "comfortable ride" can be defined as "a ride that experiences low acceleration forces", i.e. forces that are not large enough to change the shape of the more liquid parts of the driver or passenger's body; nor require them to use excessive muscle force to stay in one place; nor to disorientate them.

An important factor of safe driving is hazard perception and prediction. A driver who is good at this can avoid making sudden movements and therefore avoid producing high acceleration forces.

If is also worth noting that other road users can more easily predict the progress of a smooth driver. The definition of smooth in acceleration terms could arguably be the more complex -a low rate of change of acceleration', but irrespective of that, sudden and jerky driving generally produces acceleration forces that are relatively large.

All the time that the vehicle is experiencing an acceleration force, energy is being used and components are being worn out. The amount of energy and wear is proportional to the size of the acceleration.

When driving for speed, a vehicle's stability at any given moment is governed by the amount of grip the tyres have on the road, i.e. the amount of acceleration they can experience before they loose grip.

To keep this point as high as possible a driver must learn to minimise weight transfer', which means the driver must keep the vehicle's weight evenly distributed over the vehicle's tyres. The driver does this by choosing a good driving line and carefully controlling the brake and throttle. Weight transfer is the direct result of experiencing an acceleration force. Having the ability to guide a vehicle in a line that produces low acceleration forces means that one has room to increase speed.

To summarise, learning to drive with low acceleration forces is learning to drive well. Although an acceleration force could be detected with a mechanism as simple as a pendulum, conservation of momentum in the pendulum would soon render it un-interpretable in practice.

Drivers require that the information be presented as simply as possible in order to concentrate attention on the road ahead.

Electronic devices already exist but they are complex and most are designed to assess engine performance rather than giving the driver immediate feed back on the quality of their driving.

An object of this invention is to provide a means for the occupants of a vehicle to quantify the acceleration forces that the vehicle experiences.

Accordingly this invent ion provides an in-vehicle accelerometer that senses acceleration forces in one or more directions parallel to the ground, in which the force sensors, consisting of sprung-loaded weights, can dissipate any conserved momentum they contain, and information about the acceleration forces experienced is presented to one or more occupants of the vehicle in a readily accessible manner.

Preferably the accelerometer is an entirely mechanical device, relying solely on the energy created by the vehicle in which it is placed.

However, it may be fitted with electronic sensors, amplifier circuits and microprocessors which would provide the means to record data from a journey and extrapolate data such as the rate of change of acceleration and average, high or low figures for a journey. The addition of electronic components would also provide the means for an illuminated display and audio feedback such as a buzzer.

Preferably all the weights would push against one single spring so that the movement in the spring would represent the sum of the acceleration forces in any direction and the user would only have one measurement to consider. However, in some circumstances, the more experienced user may prefer individual readings for every direction measured (e.g. forwards backwards left and right; or four readings representing the loading on each wheel). In this case each weight Specific embodiments will now be describe by way of example with reference to the following drawings: Fig. 1 Front view -Full assembly.

Fig. 2 Right side view -Full assembly.

Fig. 3 Isometric view, front top right -Full assembly.

Fig. 4 Front view -Showing position of global axes and Centre Point (1) in relation to Body (2) and Bezel (3).

Fig. 5 Right side view -Position of global axes and Centre Point (1) in relation to Body (2) and Bezel (3).

Fig. 6 Isometric view, front top right -Showing position of global axes and Centre Point (1) in relation to Body (2) and Bezel (3).

Fig. 7 Right side view -Showing only those components involved with the self-levelling gimbals mechanism. Body (2) and Bezel (4) are cut away to reveal the components inside.

Fig. 8 Isometric view, back top right -Showing only those components involved with the self-levelling gimbals mechanism in relation to global X/Y/Z axis. Body (2) and Bezel (4) are cut away to reveal the components inside.

Fig. 9 Isometric view, back top right -Showing only those components involved with the self levelling gimbals mechanism. Body (2) and Bezel (4) are cut away to reveal the components inside.

Fig. 10 Top view -Showing arrangement of components that make up the accelerometer mechanism.

Fig. 11 Isometric view, front top right -Showing arrangement of components that make up the accelerometer mechanism.

Fig. 12 Front view -Showing the Weights (9) and the Lever Arms (1 2).

Fig. 13 Side view -Showing a close up of the Cam (13) cut away to reveal the tips of the left hand Lever arms (12) in contact with the Cam surface (14). Also showing the Cam Spring (15); and the Needle (16).

Fig. 14 Isometric view, back top right -Showing close up A' of High Point Marker (17), the wedge profile at the tip of Needle (16), one of the Rollers (19), and a segment of the Ring (18). Bezel (4) and Dial (22) are also shown cut away to reveal both the high marker mechanism components and a section through the circular rim detail found on the front face of Dial (22). (N.B.

in most figures the Needle (16) has been shown at its rest position, 45 deg lower than horizontal, but in this figure and the figure 15 it is shown in a vertical position.

Fig. 15 Isometric view, back lop right -Showing position of close up A' shown in figure 14.

Fig. 16 Isometric view, front top right -Showing High Point Marker Actuator Cam (20) and High Point Marker Lever (21) in relation to Centre Stand (5) and Cam (13).

Fig. 17 Isometric view, back top right -Showing Body (2) and Bezel (4) cut away to reveal all internal components in place, except for Dial (22).

To help with the descriptions which follow, reference will be made to global X, Y and Z coordinates, the zero or centre point of which is Centre Point (1); Xt being left and right relative to the vehicle, Y' forwards and backwards relative to the vehicle and Z' being up and down relative to the vehicle. (See figures 4, 5 and 6).

In this example, the accelerometer comprises a Body (2) that has a curved underside and a flat upper so that it may be wedged between the windscreen and the dashboard of a vehicle. Suckers (3) are mounted at the perimeter of the flat upper side to fix the body securely to the windscreen. (See figures 1, 2, and 3).

An alternative method of fixing the body to the vehicle may be the use of adhesive or proprietary fasteners; or the unit maybe designed and built into the dashboard of the car.

For the accelerometer to measure lateral acceleration forces the accelerometer mechanism must be levelled relative to the vehicle chassis. This may be done whilst the vehicle is stationary on level ground using a self-levelling gimbals support such as the one described below. (See figures 7, 8. and 9).

Gimbals Support (6) is mounted on arms extending from the side of the body so that it can rotate about the global Y axis. Centre Stand (5) is cradled by Gimbals Support (6) so that if can rotate about the global X axis. Bezel (4) is attached to Centre Stand (5) at the Centre Stand's (5) base, and together they form a chassis on which the accelerometer mechanism is mounted. The entire chassis and accelerometer mechanism assembly is given a low centre of gravity so that the operator can be sure that, if given a few gentle taps, it will rotate about the global X and V axis on the pivots formed by the Gimbals Support (6) until the mechanism is level. In the example described in this patent, level' means when the Weight Pivots (10) are parallel to the global Z axis.

In order to be able to lock and release the gimbals mechanism, Gimbals Support (6) is also able to slide back and forth (along the global Y' axis) relative to Body (2). A Gimbals Locking Cam (7) may be turned so that it pushes the Gimbals Support (6) backwards, which in turn pushes the chassis assembly backwards. Bezel (4) has an outer surface that is spherical [the centre of which is Centre Point (1)]. When the assembly is pushed back by Gimbals Locking Cam (7) the spherical outer surface of the Bezel (4) is forced against Clamp Surface (8).

Clamp Surface (8) is a ring formed by Body (2) and centred on global axis Y. When Clamp Surface (8) and Bezel (4) are pushed together they clamp the whole assembly in the level position.

The Accelerometer Mechanism itself uses kinetic energy transferred from the vehicle to one or more weights that can roll, pivot, or slide from a dead stop. An example of an arrangement of weights will now be described. (See figures 10, 11, 12 and 13) An arrangement of the weights that consists of four Weights (9) arranged either side of Centre Point (1) mounted on vertical (parallel to the global Z axis) Weight Pivots (10) so that a line drawn (in plan) between a weight's centre of gravity and its pivot lies at 45, 135, 225 and 315 degrees respectively from a line drown down the middle of the vehicle from front to back. If one pair of weights diagonally opposite each other are able to rotate clockwise from dead stop positions, and the other pair are allowed to rotate anti-clockwise from similar dead stops, then the movement in each weight may approximately represent acceleration forces acting in the direction of one of each of the vehicles four wheels; assuming an approximately central placement of the accelerometer in the vehicle; and that the vehicle has four wheels. The weights may be shaped to surround the Dial Face (11) so that, provided the Dial Face (11) and the Body (2) are made of a translucent or perforated material, the Dial Face (11) maybe backlit by light from outside the vehicle. The Weights (9) may also be shaped to have a greater proportion of their mass below Centre Point (1) so that no extra weight need be added to ensure the proper function of the self-levelling gimbals described above.

Acceleration forces caused by the vehicle are transferred from the Weights (9) through Lever Arms (12) to Cam (13), which rotates about global axis X. The forces are transferred by the Cam (13) to Cam Spring (15).

When the acceleration forces created by the vehicle have subsided, the Cam (13), pushed by the Cam Spring (15) may push the Weights (9), via Lever Arms (12), so that they return to their dead stops. Any kinetic energy contained within the Weights (9) will be dissipated when they hit the dead stops. The dead stops should be non-elastic and placed as far from the Weight Pivot (10) as possible. When the system is completely at rest, and the vehicle is on level ground, the Cam (13) will have pushed the Weights (9) to a position where they are almost but not quite touching their dead stops; thus ensuring that the Cam (13) will be moved as soon as any friction in the system is overcome.

Cam (13) may be balanced about its pivot point so that its own mass will not be directly effected by acceleration forces created by the vehicle. Cam (13) has its maximum rotation limited so that, although it may be pushed round by more than one Lever Arm (12), it will not interfere with the Lever Arms (12) connected to any of the Weights (9) that are resting against their dead stops. The ratio of movement in the Weights (9) to movement in the Cam (13) may be made to be linear or non-linear by altering the profile of Cam Surface (14). In the example shown all the weights have equal leverage however, the Cam Surface (14) becomes progressively steeper, thus making it progressively more difficult for the Weights (9) to compress the Cam Spring (15) which results in a much more sensitive measurement of lower acceleration forces, but allows for a greater range. The same result may also be achieved with the use of a linear Weight (9) to Cam (13) movement ratio, and a non-linear Cam Spring (15).

The movement in the Cam (13) and the Cam Spring (15) represents the sum of the acceleration forces acting on the Weights (9) and may be presented to the vehicle occupants in the form of a needle dial. The Needle (16) may pivot around Centre Point (1). driven by Cam (13) using a mitre gear so that it rotates on the global Y axis. Needle (16) may be balanced about its pivot point so that its own mass will not be directly effected by acceleration forces created by the vehicle.

In order to allow the occupants of the vehicle to keep their eyes on the road ahead, a means of recording the activity of Needle (16) may be provided, an example of which will now be described. (See figures 14 and 15).

High Point Marker (17) is mounted on Ring (18) that can freely rotate on three or more Rollers (19) placed concentric to the Needle's (16) axis of rotation. This assembly may be balanced about its theoretical pivot point so that its own mass will not be directly effected by acceleration forces created by the vehicle. The High Point Marker consists of a pivot (axis parallel to global Y axis) from which a visible pointer, a foot, and an anchor spring extend. The anchor spring gently pushes the High Point Marker (17) clockwise (when viewed from the back as in Fig. 14) about its pivot so that its foot acts as a break on a circular rim mounted in the dial face. The High Point Marker's (17) visible pointer points towards the Needle's (16) axis of revolution, and extends far enough to tall into the path of the tip of the Needle (16). The High Point Marker (17) and Ring (18) are held in place by the High Point Marker's (17) foot until the Needle (16). when set in motion by the movement of the Weights (9) makes contact with the High point Marker's (17) pointer and pushes with enough force to turn the High Point Marker (17) against ifs anchor spring; thus turning its foot away from the circular rim on the Dial (22). Once friction under the foot of the High Point Marker (17) is sufficiently reduced, the High Point Marker (17) and Ring (18) assembly will slide round on Rollers (19).

A means to move the High Point Marker (17) to the beginning of the dial may be provided in order that the whole process may start again and an example of which will now be described. (See figures 16).

The user may turn High Point Marker Actuator Cam (13) so that it pushes on a High Point Marker Lever (21) mounted on the Centre Stand (5). The High Point Marker Lever (21) forces the Cam (13) to turn, as if being pushed by the weights, so that it turns the Needle (16) far enough to push the High Point Marker (17) through a full 360 degree rotation back to its start point. The high point marker lever may be sprung-loaded so that once pressure from the high point actuator Cam (13) is released the High Point Marker Lever (21). the Cam (13), and the needle all return to their rest positions. While en route back to its rest position, the Needle (16). will come into contact with the High Point Marker's (17) pointer from the opposite side, thus increasing the pressure on the High Point Marker's (17) fool and increasing the friction holding the High Point Marker (17) in place. The Needle (16) may be given a wedge profile in order to slip past the High Point Marker (17) pointer, either in front or behind it.

The activity of Needle (16) may also be recorded by an indexing counter of known invention that counts the number of times Needle (16) moves beyond a given point.

It may be useful for the driver of the vehicle to be made aware of how weight is being transferred between the vehicles wheels. This may be done with the use of Flags, one for each weight. Each Flog may latch on' or off' when its respective weight (9) moves away from or back towards its respective dead stop. The flags may be balanced about their pivot point so that acceleration forces created by the vehicle will not directly affect their own weight.

A second embodiment of an in-vehicle accelerometer may be one that indicates weight transfer to each wheel. This maybe achieved with an accelerometer much like the one described above, but where each Weight and lever arm acts against its own Cam and Cam spring assembly. The movement in each of the springs may be individually presented to the vehicle occupants in the form of similar needle dials as described before.

A third embodiment of an in-vehicle accelerometer may be one that indicates weight transfer between the front and back wheels. This maybe achieved with an accelerometer much like the one described above, but where the weights act in pairs on two spring-loaded cams.

The weights pivoting forward would push on one cam, and the weights pivoting backwards on the other. Alternatively, the number of weights maybe halved so that only one moves forward and one moves backward; each weight having its own cam and display arrangement.

In some driving conditions. e.g. very bumpy terrain, the Needle (16) described in the examples given above, may move too rapidly to be easily seen. A dampening effect may be achieved by substantially increasing the mass of Needle (16) in relation to other components, so giving it greater inertia.

For some drivers, the Needle and Dial arrangement may be too much to concentrate on whilst driving. An alternative display may be used that is more easily seen out of the corner of ones eye. The display may consist of highly contrasting colours, where the relative proportions of the surface areas of the colours is proportional to the displacement of the springs against which the acceleration force-sensing weights push.

The contrasting display may be an aperture that opens to reveal a highly contrasting background; the size of the aperture being mechanically linked to the displacement of the springs against which the acceleration force-sensing weights push.

In order to account for different driving conditions, or different levels of driving skill, it may be necessary to adjust the sensitivity of the accelerometer. This may be done by altering the amount of leverage that the spring has for returning the cam and weights to the rest point; or alternatively replacing the spring with one of a higher or lower N/rn rate.

Claims

Claims 1. An in-vehicle accelerometer that senses acceleration forces

in one or more directions parallel to the ground, in which the force sensors.

consisting of sprung-loaded weights, can dissipate any conserved momentum they contain, and information about the acceleration forces experienced is presented to one or more occupants of the vehicle in a readily accessible manner.

2. An accelerometer as claimed in claim 1 that senses acceleration forces in four directions parallel to the ground: Iwo opposite directions in two perpendicular planes.

3. An accelerometer as claimed in claim 1 or claim 2 where the sensors of the acceleration forces consist of individual weights for each direction to be measured that can swivel, slide, or roll with minimum friction in one direction only from stop barriers which, when hit by the sensor, can dissipate the sensor's kinetic energy.

4. An accelerometer as claimed in claim 3 where all the weights used for sensing the acceleration forces are returned to their stop by means of levers connecting to a single spring, so that a weight cannot move without hitting the spring but the spring may be moved by one or more weights such that this movement has no effect on the weights being forced against their stops; thus allowing movement in the spring to represent the sum of the forces acting on all the weights.

5. An accelerometer as claimed in claim 4 where the displacement of the spring is translated by means of gears and levers to a visual display in the form of a pointer on an analogue dial.

6. An accelerometer as claimed in claim 4 where the displacement of the spring is translated by means of gears and levers to a visual display in the form of an adjustable aperture that opens to reveal a

contrasting background.

7. An accelerometer as claimed in claim 4 where the displacement of the spring is translated by means of gears and levers to a visual display in the form of contrasting indicator progressively protruding from a concealed compartment.

8. An accelerometer as claimed in claim 5, claim 6, or claim 7 where the relationship between the force applied by the acceleration force-sensing weights and the movement in the visual display is made to be non-linear by the use of a cam mechanism to link mechanically the movement in the acceleration force-sensing weights and the displacement of the spring.

8. An accelerometer as claimed in claim 5. claim 6, or claim 7 where the relationship between the force applied by the acceleration force-sensing weights and the movement in the visual display is made to be non-linear by the use of a spring assembly with a non-linear deflection.

9. An accelerometer as claimed in any preceding claim where it is possible to adjust the mechanical advantage created in the system that links the movement of the weights to the movement of the display, so adjusting the proportion between the force sensed by the weights and the movement in the visual display.

10. An accelerometer as claimed in any preceding claim where the upper limit of the visual display's movement is registered by a marker that is held by just enough friction to keep it in place unless it is moved further by the pointer, aperture or indicator, or by user intervention.

11. An accelerometer as claimed in any preceding claim where a counter can be set to count every time the visual display moves beyond a given point.

13. An accelerometer as claimed in any preceding claim where the movement of the individual acceleration force-sensing weights is displayed either directly or by connection to signal levers so that the occupants of the vehicle may assess in which direction the acceleration forces are working.

14. An accelerometer as claimed in any preceding claim where the moving components in the visual display are balanced but made to have a mass substantially greater than the other components in the mechanical system, excluding the acceleration force-sensing weights, thus giving the moving components in the visual display a relatively high inertia and creating a dampening effect on the movement in the system.

15. An accelerometer as claimed in any preceding claims where the acceleration force-sensing weights are arranged in a vertical ring around the edge of the dial or display, shielding the dial or display from being reflected in the windscreen of the vehicle.

16. An accelerometer as claimed in any preceding claims where a suction cup is provided to attach the instrument to any smooth surface on the vehicle.

17. An accelerometer as claimed in any preceding claims where an adhesive strip is provided to attach the instrument to any surface on the vehicle.

18. An accelerometer as claimed in any preceding claims where the display is translucent allowing it to be backlit by any light outside the vehicle.

19. An accelerometer as claimed in any preceding claims where the whole acceleration and display system is mounted, using a lockable rotating mechanism that allows rotation in at least two planes (i.e. gimbals), to a body or frame which is in turn mounted to the vehicle; thus allowing the system to be easily set level in relation to the vehicle body.

20. An accelerometer as claimed in the preceding claim where the acceleration force-sensing weights have a centre of gravity lower than the centre of the gimbals location so that the mechanism will level itself.

21. An accelerometer as claimed in all preceding claims where electronic sensors are attached to the moving parts so that electronic data can be obtained.