GB2516619A

GB2516619A - Land wheeled drone

Info

Publication number: GB2516619A
Application number: GB1310723.0A
Authority: GB
Inventors: Dennis Majoe
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-06-17
Filing date: 2013-06-17
Publication date: 2015-02-04
Also published as: GB201310723D0

Abstract

A land based drone with at least one wheel 1,2 that can move forwards and backwards and can traverse uneven terrain due to actuated changes in its centre of gravity and multi segmented axle 5,6,7. The centre of gravity of the drone falls beneath the axle when at rest, is forward of the axle when the drone is moving forwards and is to the rear of the axle when moving backwards. The wheels have independent drive assemblies and can rotate in opposite directions to facilitate turning. The drone can dynamically sense changes in acceleration and rate of turn about three axes to enable it to maintain a desired heading and to enable it to adjust its centre of gravity so that it can climb a stair. The actuation of the articulated axle is carried out by means of pneumatic air muscles. The spokes of the wheels are sprung in the plane of the wheel to provide shock and vibration suspension.

Description

Land Wheeled Drone This invention relates to a land wheeled surveillance drone.

In many emergency services situations it is necessary to provide surveillance using cameras or other sensors and tools that may be transported to a sensitive location. However these drones tend to lack agility, have large turning circles, cannot climb stairs or drive over rocky terrain. Those drones that can negotiate bad terrain or stairs have features such as tracks or are serpent like and these features do not allow fast on the road locomotion.

An alternative is to use a lightweight wheeled drone with deformable wheel axis and active counterbalance to overcome these limitations.

The present invention proposes a single or dual wheel drone where each wheel is directly motorised. The wheel motors mount onto an actively actuated platform which can change the relative position of the wheels' axes and change the position of the drone's centre of gravity.

A single wheeled drone having a direct motorised drive to the wheel axle where the centre of gravity of the drive assembly and wheel falls beneath the height of the wheel axle is inherently stable at rest when compared to other single wheeled devices. In order to generate a torque to move the wheel forward or backwards the centre of gravity must be moved above the rest position and forward or rearward of the wheel axis.

To incorporate additional stability and turning ability a dual wheeled drone may operate similarly as the single wheeled drone but with two wheels positioned at the two ends of a fixed common axle. With independent drive to each wheel the drone may be made to rotate with zero radius of turn, making it extremely nianoeuvrable. Additionally since the wheels are co-axial unlike a conventional bicycle, the turning moment about the vertical axis is smaller than a bicycle or tricycle or quad wheel drone with the same size wheels.

When the common axis or axle is replaced by a multi segmented structure comprising a multi-degree of freedom articulated and actuated assembly to which the power drive to each wheel is mounted then the axle of each wheel may be made to move independent of the other. This allows the drone to behave with greater dexterity when traversing difficult terrain such as large rocks and debris and heavily sloped or cambered roads.

Additionally the drone further benefits if one part of the articulated assembly is automatically actuated so as to be kept stable relative to the wheel axis or the ground and another part of the articulated assembly automatically actuated to move to desired different points in space so as to cause a change in the drone's centre of gravity or to position a load. The advantage of this is that the stable part of the structure forms a safe platform for mounting sensitive equipment and surveillance sensors while the moving part provides the shift in the centre of gravity or load.

When the drone positions the centre of gravity near to, or outside of, the outline of the circumference of wheels this provides the drone a posture which facilitates the drone to climb high obstacles such as stair steps and large rocks due to the fact the centre of gravity may be positioned beyond the contact of the wheel and the obstacle and provided the counter balance outweighs the wheel section, the drone will pivot over and climb the obstacle.

When moving along a desired path the drone may be forced off the desired direction due to variations in drone mechanics or debris or uneven surfaces in the road. Therefore the invention incorporates a computer and dynamic sensing of acceleration and rate of turn in three axes. Using this motion feedback in a closed control loop the computer provides control signals to actuate the multi-segment structure and to power the drive motors to maintain desirable speed, and yaw, roll and pitch angles.

Preferably, the drone has two wheels each driven by an electric motor.

Preferably, the drone has a multi segmented, hinged and actuated platform the side segments of which attach the wheel motors.

Preferably, the drone's multi segmented, hinged and actuated platform has a centre segment which links the two hinged side segments and also couples to the third and final segment.

Preferably, the drone's final segment hinges onto the central segment and carries at the opposite end the battery and other components that all contribute significantly to the weight of the overall drone and act as a counter weight.

Preferably, the drone has a computer to compute the optimal positioning of the segments and the directional sense and drive power output to each motor.

The computer preferably includes accelerometer sensors, rate gyro sensors, segment angular position feedback and radio communications to a base station and human controller.

The computer preferably executes a control algorithm that modifies the drive to the motors and the plurality of actuated segments so as to achieve controlled locomotion in different demanding environments.

An example of the invention will now be described by referring to the accompanying drawings: Figure 1 shows a drone comprising two wheels, the wheel motors and the multi segment platform.

Figure 2 shows the side view of the drone when at rest and the third segment is actuated to rest within the drone, such that the overall centre of gravity is below the wheel axis.

Figure 3 shows the side view of the drone as it moves forward, the central segment remaining horizontal due to the torque applied to the wheel motors, the third segment actuated forward shifting the centre of gravity forward and balancing the torque applied to the wheels.

Figure 4 shows the frontal view of the drone when the side segments are actuated to different angles relative to the central segment, such as when the drone is traversing a slope or heavily cambered road or when a wheel goes over debris, while keeping the central segment horizontal.

Figure 5 shows the side view of the drone as it climbs a stair, the third segment actuated well forward of the wheel so that the drone tips up the stair pivot point.

Figure 6 shows the manner in which two air muscles are used in antagonism to drive a hinged joint using feedback from a curvature or bend sensor In figure 1, each of the drone wheels land 2 connect to an electric motor 3 and 4. The spokes of the wheels are preferably made of flexible materials with deformation restricted to within the plane of the wheel to provide suspension.

Motors 3 and 4 are assembled to one end of side segment sections 5 and 6.

The other end of segments 5 and 6 are hinged to a central segment section].

Air muscles 8, 9, 10 and 11 ensure that the segments S and 6 may be actuated to a controlled hinging angle between S and 7 and 6 and 7. Hinging angle is sensed by bend rotation sensors 12 and 13.

Segment 7 supports a final segment section 14 one end of which is hinged to segment] and the other end 16 includes a compartment that holds the system battery pack, air pressure pump and air flow valves, forming a counter weight. Two air muscles 17 and 18 are applied between segments 7 and 14 such that the hinging angle between segments 14 and 7 may be maintained at a desired angle. The angle may be monitored by bend rotation sensor 15.

Figure 6 shows the operation of the antagonistic air muscles. Air muscles are preferably used in order that the hinged joints are as light weight as possible, while the associated mass of the air pump that drives them may be located in 16. The air muscles may be temporarily locked such that they provide forces while no energy is applied leading to energy saving and air muscles naturally combine spring and damper actions in the locked state.

All air muscles are inflated and deflated using the air flow control valves and air supplied from the air pressure pump. The air flow valves and air pump are driven by the control computer such that there is an inflation or deflation of the air muscles to achieve desired hinge angles monitored by the computer using the feedback from 12, 13 and 15.

When at rest the segments are actuated and remain in position as shown in figure 2. In this position the centre of gravity is designed to sit below the axis of the wheels with the central multi segment platform hanging horizontal.

When the drone is to be moved in a forwards direction, depicted as the right hand side in figure 3, the final segment 14 is actuated forward in the position as shown in figure 3. In this position the centre of gravity is forward of the axis of the wheels and in the case as shown with the central multi segment platform horizontal, there will result a torque applied to the wheels which creates a rearwards thrust and forward motion.

When the drone is on a slope or cambered road, the drone will roll relative to the vertical.

By driving the actuators 8, 9, 10 and 11 the side segments will rotate relative to the central segment. As a result the drone wheels will be at different heights as shown in figure 4 and the central segment will be maintained horizontal in roll.

To combine the features of a horizontal central segment in pitch and roll, as well as achieve rearward or forward thrust and maintain a desired directional path, the invention preferably applies a three layer control algorithm which aims to keep the horizontal state of the central segment by sensing the platform angle relative to the earth's gravity using an accelerometer.

In a first control algorithm the accelerometer in the computer device on the central segment is used to sense the platform horizontal state in pitch and roll. The computer will drive the actuators 8, 9, 10, 11 to stabilise the platform in roll by pushing the wheels up or down on either side.

In a second control algorithm the computer device will drive motors 3 and 4 to regulate the platform in a horizontal position in pitch.

If the platform is horizontal in pitch and roll and the reactionary centre of gravity is below the wheel to wheel axis, then the drone will not experience any forward thrust. However if the reactionary centre of gravity is forward of the axis the drone will deliver a rearward thrust and similarly but opposite for forward thrust or braking action.

Therefore with the first and second algorithms applied, the forward and reverse motion of the drone is accomplished by actuating the final segment and counter weight forward or backward as shown in figure 3. When actuated forward, the centre of gravity shifts forward and would result in the central segment pitching down. However as the motors 3 and 4 are actuated to counter this therefore a rearward thrust is obtained.

When the drone is to travel forward or backward along a straight path, debris on the path or differences in motor torque will result in the drone turning off the desired heading. In a third control algorithm, the rate of turn of the platform in yaw is sensed using a rate of turn gyro sensor in the computer device. If the drone is turning away from the desired heading it will modify the electrical power drive to the motors 3 and 4so as to cancel yaw rotations.

When the above algorithms are executing, modifications in the position of the counter balancing weight of 16 is used to change thrust while balancing of the drone in pitch, yaw and roll is maintained.

To change direction the speed of the left or right wheel is changed so that the slower wheel is overtaken by the faster wheel resulting in an effective change in direction of travel.

In order to climb stairs 19, without the benefit of available forward momentum, where each step up height is less than the wheel radius, it is preferable to bring the drones overall centre of gravity as close as possible to a point equal or a little past the step corner 20. This can be achieved by a combination of rotations of the support sections. Provided a good frictional grip is maintained at the step corner, this will act as a natural pivot and the wheel will rock forward of the pivot and thereby climb the step.

If the step up height is more than the wheel radius it is impossible for the wheel to climb the step face. In this case the arm is extended over the step corner and once the centre of gravity is beyond the step corner, the arm may pull the wheels over the corner and onto the step.

Claims

Claims 1. A wheeled drone comprising a wheel and a direct drive assembly connecting and applying torque to the wheel axle where the centre of gravity of the drive assembly falls beneath the wheel axle when the drone is at rest and where the centre of gravity of the drive assembly moves forward of the wheel axle when the wheel is rotated in forwards motion and where the centre of gravity of the drive assembly moves to the rear of the wheel axle when the wheel is rotated in rearwards motion.
2. A wheeled drone as in claim 1 that comprises two wheels interconnected co-axially by a central drive assembly the centre of gravity of which falls beneath the wheels' axle when the drone is at rest and applies torque to either wheel where the centre of gravity of the drive assembly moves forward of the axle to move forward and where the centre of gravity of the drive assembly moves to the rear of the axle to move rearwards and the wheels can be driven in opposite rotational directions such that the drone may turn clockwise or anti-clockwise around a vertical axis.
3. A drone as in claim 2 that comprises two wheels whose axles and independent direct drive motors are mounted on opposite ends of a multi-degree of freedom articulated and actuated assembly such that the axle and motor of one wheel may be positioned in a variety of positions and directions relative to the axle and motor of the other wheel.
4. A drone as in claim 3 where one part of the articulated assembly is automatically actuated so as to be kept in a stable position relative to the axis adjoining wheel centres or the ground and another part of the articulated assembly is automatically actuated to different positions to cause a change in the drone's centre of gravity or to position a load.
5. A drone as in the above claim 4 that will position part of the articulated assembly outside of the outline of the circumference of wheels.
6. A drone as in the above claim 5 that will maintain the desired heading of the drone incorporating dynamic sensing of acceleration and rate of turn in three axes, drive actuation and control logic to be able to maintain desired yaw, roll and pitch angles.
7. A drone as in claim 6 that incorporates dynamic sensing of acceleration and rate of turn, drive actuation and control logic to be able to cause a pivoting motion of the drone over the edge of a stair, such that the forward section of the drone tips over the edge thereby allowing the wheels to climb the stair.
8. A drone as in the above claims in which air muscles are used to implement actuation in the articulated and actuated assembly and in which the spokes of the wheels are sprung in the plane of the wheel to provide shock and vibration suspension.