GB2542602A

GB2542602A - A robotic device

Info

Publication number: GB2542602A
Application number: GB1516960.0A
Authority: GB
Inventors: Davies Aidan; O'connor Padraig
Original assignee: Reamda Ltd
Current assignee: Reamda Ltd
Priority date: 2015-09-25
Filing date: 2015-09-25
Publication date: 2017-03-29
Also published as: GB201516960D0

Abstract

The invention relates to a robotic vehicle 10 having six wheels 12-15 and three axles, whereby the driven middle axle and wheels are positioned lower than the front and rear wheels to optimise turning. Further to improve the vehicles hill climbing capability the rear axle and wheels 12 & 13 are pivoted by an actuator connected through a control with inclinator to bring the rear wheels into contact with the surface to be climbed, improving overall traction, and when laden used as a counterbalance.

Description

A robotic device

This invention relates to a robotic device and, in particular, to a robotic device having three sets of wheels. A typical six wheeled robotic device has three sets of wheels, two rear wheels, two middle wheels and two front wheels, with three wheels being on the left-hand side of the robotic device and three wheels being on the right-hand side.

For optimum turning on a six wheeled robotic device, the middle wheels are placed lower than the front and rear wheels. When performing a skid steer tum/tank turn on a horizontal surface (e.g. left wheels going forward, right wheels in reverse), as the middle wheels are lower the robotic device can rock, as not all wheels are in contact with the surface at the same time. Thus, the resistance to turning is reduced in comparison to a robotic device having all wheels at the same level.

Whereas, turning of the robotic device is assisted by having the middle wheels lower, when the robotic device attempts to climb a slope, not all wheels will be on the surface at the same time, so the climbing efficiency of the robotic device is reduced. This is due to the fact that all of the wheels are not providing traction together.

For a six wheeled robotic device to climb a steep slope all of the wheels must be in contact with the surface at all times, so as to provide maximum traction. When all wheels are in contact with the surface the average pressure on the wheels is passively equilibrated and this improves motion capability and climbing torque.

However, when the robotic device, having the middle wheels lower than the front and rear wheels, makes contact with a slope to be climbed, the rear wheels will either not make contact with the surface or if the weight of the robot is to the rear of the vehicle, the front wheels will not make contact with the surface. This greatly inhibits the climbing ability of the robotic device.

Another disadvantage of this type of robotic device is that, on reaching the top of a slope, a see-saw effect occurs, which can be dangerous for the robotic device, as the robotic device will drop down hard on the surface once it overcomes the slope. When the robotic device reaches the top of the slope the front wheels will rise into the air. Thus, the robotic device will be in a very unstable position at the top of the slope.

Thus, with a rigid vehicle structure it is impossible to keep all six wheels of the robotic device on the surface at all times when attempting to climb a slope.

To overcome the limitations of the robotic device, having the middle wheels lower than the front and rear wheels, designers of robotic devices have added a dropping back axle to a six wheeled robotic device. The back axle, in such a device, is not fixed and can drop a number of degrees, gravity assisted, to make contact with a slope, when climbing.

However, a disadvantage of introducing a gravity based dropping back axle is that four wheels will now contact the surface, when the robotic device is on a horizontal surface. Thus, the advantage of having lower middle wheels for turning is negated.

Another major disadvantage of the robotic device having a gravity assisted dropping back axle is that when the robotic device is lifting a heavy weight to the front thereof, as the back axle is not a rigid structure it cannot be used as a counter balance to the extra weight to the front of the robotic device.

With a critically heavy weight in front of the robotic device, on a rigid structure the rear wheels act as a counter balance and help the stability and increase lifting capabilities of the robotic device. With a dropping back axle, as the weight lever increases in front of the robotic device, there is no counter-balancing effect by the rear wheels, as the dropping back axle will lower towards the surface, if the robotic device starts to lean forward.

It is an object of the present invention to overcome the disadvantages of the robotic devices hereinbefore described.

Thus, the invention provides a robotic device comprising a body section, two rear wheels, two middle wheels and two front wheels all attached to the body section, with three wheels being disposed to the left-hand side of the body section and three wheels being disposed to the right-hand side of the body section, and with the middle wheels being positioned lower than the front and rear wheels with respect to a surface on which the robotic device sits, in use, with the rear wheels being attached to a rear axle, which rear axle is attached to the body section, such that the rear axle is movable relative to the body section to provide optimum wheel contact with the surface regardless of the slope of the surface.

An advantage of the robotic device according to the invention is that, the robotic device controls the position of the rear wheels relative to the surface at all times. This provides optimum wheel contact with the surface for all situations.

Preferably, the rear axle is movable relative to the body section by means of an actuator.

An advantage of this aspect of the invention is that an actuator can move the position of the rear axle in a steady and smooth fashion.

Further, preferably, a control unit on the robotic device controls the movement of the actuator.

An advantage of this aspect of the invention is that the control unit can be programmed to change the position of the rear axle under particular sets of conditions.

In one embodiment of the device in accordance with the invention, in use, as the robotic device turns, the control unit instructs the actuator to move the rear axle to an up position, such that the rear wheels are clear of the surface.

An advantage of this aspect of the invention is that the robotic device will have minimal wheel resistance on the ground when it is negotiating a skid steer turn. Thus, there is less frictional resistance than if the rear wheels were engaging the surface.

In a further embodiment of the device in accordance with the invention, the control unit is connected to an on-board, angle detection inclinometer, which inclinometer indicates to the control unit, in use, that the robotic device is starting to move up a slope, resulting in the control unit instructing the actuator to move the rear axle into a lower, climbing position appropriate to the gradient of the slope.

An advantage of this aspect of the invention is that all of the wheels on the robotic device are forced to make contact with the surface, which results in improved climbing ability. A further advantage of this aspect of the invention is that the climbing position selecting by the control will be dictated by the gradient of the slope, which in turn is calculated by the on-board inclinometer. If the gradient of the slope changes then the climbing position of the rear axle will be adjusted accordingly.

In a further embodiment of the device in accordance with the invention, the rear axle is spring dampened to assist the passage of the robotic device over irregular surfaces.

An advantage of this aspect of the invention is that all of the wheels of the robotic device will remain in contact with the surface as the robotic device moves forward. In particular, as the robotic device transitions the top of a slope the spring damping ensures that the rear wheels remain in contact with the surface as the robotic device moves off a slope onto a flat surface.

In a further embodiment of the device in accordance with the invention, in use, when the robotic device is lifting a heavy weight to the front thereof, the control unit instructs the actuator to move the rear axle to an up position, clear of the surface, so as to act as a counterbalance to the heavy weight.

An advantage of this aspect of the invention is that the lifting capability of the robotic device is improved due to the counterbalancing effect of the raised rear axle.

The invention will be further illustrated by the following description of an embodiment thereof, given by way of example only with reference to the accompanying drawings in which:

Fig. 1 is a plan view from above of a robotic device in accordance with the invention;

Fig. 2 is perspective view of the robotic device of Fig. 1 with the rear axle detached therefrom;

Fig. 3 is a side view of the robotic device of Fig. 1 positioned on a horizontal surface;

Fig. 4 is a side view of the robotic device of Fig. 1, positioned on a slope; and

Fig. 5 is a side view of the robotic device of Fig. 1, cresting the top of a slope.

Referring to Fig. 1, there is illustrated generally at 10, a robotic device in accordance with the invention. The robotic device 10 comprises a body section 11, two rear wheels 12, 13, two middle wheels 14, 15, and two front wheels 16,17 all attached to the body section 11, with three wheels 12, 14, 16 being disposed to the left-hand side 18 of body section 11 and three wheels 13,15,17 being disposed to the right-hand side 19 of body section 11.

The middle wheels 14, 15 are positioned lower than the front wheels 16, 17 and the rear wheels 12, 13 with respect to a surface on which the robotic device 10 sits, in use (see Fig. 3 hereinbelow).

The rear wheels 12, 13 are attached to a rear axle 20 at ends 21, 22, respectively. The rear axle 20 is attached to a member 23, which member 23 is pivotally attached to each side 24, 25 of the body section 11 at positions 26, 27, respectively. A connecting bar 28 runs across the interior 29 of body section 11 and ends 30, 31 of the connecting bar 28 are attached to the member 23 at positions 26, 27, respectively. A pair of electrically operated actuators 32, 33 is mounted in the body section 11 at positions 34, 35, respectively. The actuator 32 is attached to the connecting bar 28 at position 36 and the actuator 33 is attached to the connecting bar 28 at position 37. In use, as the actuators 32, 33 are extended they push on the connecting bar 28 causing the rear axle 20 to be lifted away from the surface on which the robotic device 10 is resting or dropped onto the surface, depending on the orientation of the surface. The movable rear axle 20 thus provides optimum wheel contact with the surface regardless of the slope of the surface. A spring dampening system 38 is connected to the actuator 32 and a corresponding spring dampening system 39 is connected to the actuator 33. The spring dampening systems 38, 39 assist the passage of the robotic device over irregular surfaces.

Referring to Fig. 2 the robotic device 10 is illustrated with the member 23 detached from the body section and with the other components shown in an exploded view.

The spring dampening system 38 comprises a mounting bracket 40, a rod 41, which is positionable within the mounting bracket 40. A coil spring 42 is mountable on the rod 41, and is retainable between flanges 43, 44 of the mounting bracket 40. End 45 of the rod 41 is passable through an orifice 46 in the flange 44.

The actuator 32 is attachable to the end 45 of the rod 41 at position 47 and to the connecting bar 28 at position 36. The member 23 has upstanding arms 48, 49 to each side 50, 51 respectively, thereof. The upstanding arm 48 is attachable to the connecting bar 28 at position 26 on the body section 11, by being sandwiched between an external plate 52 and an internal plate 53, with a bearing 54 therebetween. The upstanding arm 49 is connectable in a similar way at position 27 on the body section 11.

Referring to Fig. 3, the robotic device is illustrated on a horizontal surface 60 with the rear axle 20 in the up position resulting in wheel 13 being raised off the surface 60. This raising of the rear wheel 13 allows the robotic device 10 to turn without the rear wheels 12 (not shown) and 13 contacting the surface 60, resulting in a reduction in the resistance to the turning motion.

Referring to Fig. 4, the robotic device 10 is illustrated climbing a sloping surface 61. The rear axle 20 has been dropped down to a climbing position, which forces the wheel 13 to contact the sloping surface 61, resulting in improved overall traction.

Referring to Fig. 5, the robotic device 10 is illustrated transitioning from the sloping surface 61 to a horizontal top surface 62. The rear axle has dropped further than its position in Fig. 4 such that the rear wheel 13 maintains contact with the sloping surface 61 and the middle wheel 15 and front wheel 17 have moved onto the top horizontal surface 62.

Claims

Claims: -

1. A robotic device comprising a body section, two rear wheels, two middle wheels and two front wheels all attached to the body section, with three wheels being disposed to the left-hand side of the body section and three wheels being disposed to the right-hand side of the body section, and with the middle wheels being positioned lower than the front and rear wheels with respect to a surface on which the robotic device sits, in use, with the rear wheels being attached to a rear axle, which rear axle is attached to the body section, such that the rear axle is movable relative to the body section to provide optimum wheel contact with the surface regardless of the slope of the surface.

2. A robotic device according to Claim 1, wherein the rear axle is movable relative to the body section by means of an actuator.

3. A robotic device according to Claim 2, wherein a control unit on the robotic device controls the movement of the actuator.

4. A robotic device according to Claim 3, wherein, in use, as the robotic device turns, the control unit instructs the actuator to move the rear axle to an up position, such that the rear wheels are clear of the surface.

5. A robotic device according to Claim 3 or 4, wherein the control unit is connected to an on-board, angle detection inclinometer, which inclinometer indicates to the control unit, in use, that the robotic device is starting to move up a slope, resulting in the control unit instructing the actuator to move the rear axle into a lower, climbing position appropriate to the gradient of the slope.

6. A robotic device according to any preceding claim, wherein the rear axle is spring dampened to assist the passage of the robotic device over irregular surfaces.

7. A robotic device according to any one of Claims 3 to 6, wherein, in use, when the robotic device is lifting a heavy weight to the front thereof, the control unit instructs the actuator to move the rear axle to an up position, clear of the surface, so as to act as a counterbalance to the heavy weight.

8. A robotic device according to Claim 1, substantially as hereinbefore described with particular reference to and as illustrated in the accompanying drawings.