DE19949351A1 - Wheel module with at least one wheel; has drive motor with drive shaft and steering motor to steer wheel about steering angle, where one shaft is hollow and other shaft rotates in it - Google Patents

Abstract

The module has a drive motor (110) to drive the wheel through a drive shaft (170) and a steering motor (120) to steer the wheel about a steering angle. One of the steering shaft or the drive shaft is formed as a hollow shaft, in which the other shaft is arranged so that it can rotate. Preferably, the support point of the wheel is offset laterally relative to the steering axis and transversely to the rotation direction of the wheel. An Independent claim is included for a method for electronic coupling of the wheel module to additional wheel modules.

Description

The invention relates to wheel modules with the property of combined steerability and driveability. Several of these wheel modules are used to build vehicles such as
Vehicles of all types in indoor and outdoor environments, including vehicles without a motor drive, vehicles in the disabled and healthcare sector, such as mobile transport robots for meals,
Medicines, feces, etc. mobile robots with manipulation devices
for pick-up / delivery services, patient guidance, etc.
Wheelchairs,
Stretchers,
Hospital beds,
Cleaning and cleaning machines,
mobile tripods for film cameras,
Shopping carts used in retail stores and their parking lots. Brief transport vehicles in offices and administrative buildings. This also raises the basic problem of coordinated control (electronic coupling) of the wheel modules. A new solution to the coordination problem is part of this invention.

Previously known structures for wheel modules for highly mobile Vehicles can initially be divided into two categories: Wheel modules based on special wheels and wheel modules on standard wheels. Known special wheels are e.g. B. so-called universal wheels like orthogonal wheel, Mecanum wheels [1] or double wheels [2]. These lead to vehicle vibrations and are still not for driving on rough surfaces or carpets the suitable. Most vehicles are therefore with standard wheels  equipped. To move a surface with standard wheels speed, i.e. omnidirectionality with no preferred direction of travel all wheels must be steered and at least one wheel on be driven. Known bodies for steered and drives ne wheel modules have a limited steering angle, which is either by directly through mechanical restrictions or through z. B. routed cable is limited. In addition, the so-called Offset of the wheel from the pivot point cannot be freely specified.

From the aforementioned disadvantages of the prior art the task of the present invention, a wheel module kind described above and white terzubilden that the steering angle of the wheel module arbitrary is.

The basic (or basic) structure (structure # 1) is shown in FIG. 1. It consists of the following main components:

• - Hollow shaft steering motor and hollow shaft steering gear
• - Drive motor and drive gear
• - Vertical drive shaft
• - bevel gear
• - wheel fork
• - wheel

The steering motor moves the wheel fork and via the steering gear sets a predeterminable wheel steering angle. The drive performance is from the drive motor via the drive gear and the vertical drive shaft through the hollow shaft of the steering motor and steering gear first to the bevel gear and thus transferred to the bike.

With the basic structure is almost any lateral Offset of the wheel from the axis of rotation possible. The longitudinal However, offset is initially set to zero.

Precise description of the structure of the wheel module: the drive mo Tor drives the wheel via the drive gear, thereby generating a rotary motion. The rotary motion of the drive motor is  via the drive gear and a vertical drive shaft transmit a horizontal drive shaft (= wheel axle). The ver tical and the horizontal drive shafts are via a transmission be, for example a bevel gear, connected to each other. The steering motor drives the wheel fork via the steering gear, he thus testifies to the steering movement. The rotation of the steering motor is via the steering gear and a vertical, cylindrical Transfer the steering shaft to the wheel fork. Inside the cylinder Shaped steering shaft, the drive shaft is rotatably arranged.

On the one hand, the advantage of the new wheel modules is that they are free Predeterminability of the offset of the wheel from the pivot point. On the other hand the steering angle can be without any limitation, i. H. With Angle of rotation n. 360, set freely. So that can be different complex vehicle types with very simple tricycle kinematics to omnidirectional and surface-moveable types with a wheel module concept.

To set up any lateral and longitudinal offset, the set-up shown in FIG. 2 (set-up # 2) is given. This expansion is achieved by introducing an additional gear, for example a toothed belt gear.

In order to additionally reduce the overall height and also keep the center of gravity as low as possible, the structure shown in FIG. 4 (structure # 3) is specified. The motors are suspended, which is achieved by introducing two additional gears, for example toothed belt gears.

In all three superstructures, the steering drive works through the movement tion of the wheel fork also an undesired drive movement of the Wheel. A decoupling control affects this unwanted effect drive movement by appropriate control and actuation of the drive motor. The goal is that the vertical Drive shaft coincides with the steering movement of the wheel fork is rotated.

Description of the coordination of several bike modules

Several of these wheel modules according to the structure described above are used to build vehicles. Generally who used the N steered wheels, of which M pieces (M smaller or N) are equipped with an active tunneling. This gives the vehicles the ability to be omnidirectional Locomotion, d. H. Translation speeds and rotations speed can be specified independently of one another.

We differentiate between two applications: The vehicle controlled automatically (by a computer) or by a user zer led. Mobile robots fall into the first application. in the second use case is shopping cart, roll chairs and hospital beds. In the second application, ex internal forces compensated by steering and propulsion. So that can the user z. B. heavy objects without great effort push. The steering direction can either be entered can be specified or results from compensation of external Powers. External forces can be measured either by external forces Force sensors, moment sensors in the wheels or by electricity measurement on the motors.

It is a special mode of operation in all applications possible, in which the vehicle is on a predetermined translatory orbit and the rotation of the vehicle around the vertical axis can be freely specified. With a large ratio from rotation to translation speed can be great steep gradients are overcome or large pushing forces are exerted practice.

The individual wheels are not mechanical among themselves, son electronically coupled. Taking electronic coupling understood here that the steering and drive torques such a be made that an attachment of the wheel modules to arbitrary locations on a vehicle chassis.

The coordination is described below for the illustrated in Fig. 3 and Fig. 4 the case of wheel modules with the selected zero lateral and longitudinal offsets, but is valid accordingly for the general case.

To ensure a sensible driving operation, intersect the normals of the wheels at one point. This point represents the current turning center around which the vehicle is located currently moving on a circle. Furthermore, the propulsion speeds and moments of the individual wheels in one relationship determined by the current configuration who are. In this sense, meaningful driving means: a pure rolling of the wheels without lateral or lon longitudinal slip. Ensuring a turning center and which provides torque / speed ratios in propulsion generally not a problem if the wheels are mechanically ge are coupled. With an electronic coupling of the wheels against can, however, especially if the Center of rotation relative to the vehicle significant deviations from Ideally arise.

The reason for this is the limited speed and acceleration of the motors responsible for adjusting the steering angle position. This means that only certain steering angle ranges can be reached at the next sampling time k + 1 for a specific current steering angle speed at the sampling time k, see FIG. 6. These limits are calculated from a dynamic system model of the steering drive.

The coordination of several wheel sets is based on the following principle: When considering several wheel modules, convex polygonal areas result from intersection formation, which characterize the set of all accessible turning centers, see Fig. 7. The calculation of the turning center from the set of all accessible turning centers, which is based on to be specified even closer to the desired turning center (and the current turning center) is a special nonlinear optimization task with inequality constraints.

There are four methods of calculating the optimal rotation specified that are used depending on the application the.

Case 1 : Setting the desired center of rotation as quickly as possible

To set the desired turning center as quickly as possible, the distance between the target turning center and a turning center is minimized from the set of all possible turning centers. The optimal turning center lies either on an edge or on a corner of the convex polygon, which characterizes the set of all possible turning centers, cf. Fig. 7.

Case 2 : Setting the desired center of rotation as quickly as possible under the constraint of limited torques

If the torques from the application are limited to values smaller than the maximum torques, the method from case 1 is applied accordingly to a reduced polgonal area.

Case 3 : Energy-saving setting of the desired center of rotation

In this case, a turning center is possible from the set of all Chen turning centers sought, which is a short distance from desired turning center, but a measure of the motor mo elements (e.g. their sum) keeps them low. This is a multi-criteria rial optimization problem, the solution to a compromise between setting the turning center as quickly as possible and mi minimal energy consumption.

Case 4 : Calculation in the Cartesian range of motion of the vehicle

Cases 1 to 3 can also be solved analogously after a transformation of the polygonal area of the possible turning centers in the (three-dimensional) Cartesian movement space of the vehicle. However, the inequality constraints become nonlinear.

Embodiment Wheel modules for a highly mobile mobi len service robot with manipulation device

Fig. 8 shows a mobile service robot with Manipulationsein direction. In order to achieve a high degree of mobility, the robot is equipped with four wheel modules in accordance with the structure described above (cf. detailed image in FIG. 9).

Drawings of the wheel module used (side view Frontán view and top view) in Fig. 10 to Fig. 14. Fig. 15 and Fig. 16 show a perspective view.

The following publications have been cited in this document:
[1] U. Rembold, R. Dillmann, Mobile Manipulator KAMRO, Institute for Real-Time Computer Systems & Robotics (IPR), University of Karlsruhe, http://wwwipr.ira.uka.de/nassal/kamro-page.html .
[2] FG Pin, SM McKillough, A New Family of Omnidirectional and Holonomic Wheeled Platforms for Mobile Robots, IEEE Transactions on Robot ics and Automation, Vol. 10, No. 4, pp. 480-489, 1994.
[3] Harmonic Drive Product Guide, Harmonic Drive Antriebstechnik GmbH, Hoenbergstrasse 14 , D-65555 Limburg / Lahn, GERMANY and Harmonic Drive Systems Inc., 89 Cabot Court, Hauppage, New York, NY 11788, USA. Fig. 1
Basic structure of the wheel module. a) Side view. b) Before the view.
110 drive motor
120 hollow shaft steering motor
130 wheel fork
140 wheel
150 drive gears
160 hollow shaft steering gear
170 Vertical drive shaft
180 wheel axle = horizontal drive shaft
190 bevel gearbox
Fig. 2
Structure of the wheel module with freely adjustable lateral and longitudinal offset. a) Side view. b) Front view.
210 drive motor
220 hollow shaft steering motor
230 wheel
240 Longitudinal offset O _long
250 drive gear
260 hollow shaft steering gear
270 vertical drive shaft
280 Horizontal drive shaft
290 toothed belt transmissions
295 Lateral offset O _lat
Fig. 3
Structure of the wheel module with freely adjustable lateral and longitudinal offset according to FIG. 2 with offsets chosen to be zero. a) Side view. b) Front view.
310 drive motor
320 hollow shaft steering motor
330 wheel
340 drive gear
350 hollow shaft steering gear
360 vertical drive shaft
370 toothed belt transmission
Fig. 4
Structure of the wheel module with freely adjustable lateral and longitudinal offset. The motors are also suspended. a) Side view. b) Front view.
410 Additional toothed belt gear
420 steering motor
430 drive motor with drive gear
440 wheel
450 hollow shaft steering gear
460 toothed belt transmission
Fig. 5
Definition of lateral and longitudinal offset of a wheel with respect to its axis of rotation.
510 axis of rotation
520 wheel fork
530 wheel axle
540 wheel
550 Lateral offset O _lat
560 Longitudinal offset O _long
Fig. 6
Attainable steering angle positions for a single wheel module based on the current steering angle and current steering angle speed.
610 axis of rotation of the wheel
620 wheel coordinate system
630 wheel standards at the time of sampling
Fig. 7
Quantity of all accessible turning centers and target turning centers (example for the electronic coupling of three wheel modules and turning center outside the reachable area).
710 bike 1
720 bike 2
730 bike 3
740 target turning center
750 set of all accessible turning centers
Fig. 8
Exemplary embodiment: highly mobile mobile service robot with manipulation device.
Fig. 9
Exemplary embodiment: detailed view of the attachment of the wheel modules to the highly mobile mobile service robot with manipulation device.
Fig. 10
Technical drawing for the embodiment of a wheel module: view from the front.
Fig. 11
Technical drawing for the embodiment of a wheel module: rear view.
Fig. 12
Technical drawing for the embodiment of a wheel module: view from the left.
Fig. 13
Technical drawing for the embodiment of a wheel module: view from the right.
Fig. 14
Technical drawing for the embodiment of a wheel module: top view.
Fig. 15
Perspective drawing for the execution example of a wheel module: view from above.
Fig. 16
Perspective drawing for the execution example of a wheel module: view from below.

Claims (16)

1. Wheel module with at least one wheel, for steering and driving the wheel (see. Fig. 1 to Fig. 4), characterized by

• - A drive motor for driving the wheel via a drive shaft,
• a steering motor for steering the wheel via a steering shaft,

wherein the steering shaft or the drive shaft is designed as a hollow shaft in which the drive shaft or the steering shaft is rotatably arranged. 2. Wheel module according to claim 1, characterized in that the bearing point of the wheel is offset by a lateral offset relative to the steering axis and transversely to the direction of rotation of the wheel (see. Fig. 1 to Fig. 5). 3. Wheel module according to claim 1 or 2, characterized in that the support point of the wheel is rela tively offset by a longitudinal offset to the steering axis and in the direction of rotation of the wheel (see. Fig. 1 to Fig. 5). 4. A method for the electronic coupling of at least one wheel module according to one of claims 1 to 3 with further wheel modules according to one of claims 1 to 3 or with a wheel module with steering motor and steering shaft, but without wheel drive, characterized in that
a turning center required for driving is determined,
it is checked whether the determined turning center lies within a convex polygon that characterizes the set of all allowed turning centers and, if the determined turning center lies outside the convex polygon, the determined turning center is placed on a point on the edge of the convex polygon. 5. The method according to claim 4, characterized in that the amount of turning centers allowed depending on the maximum speeds and torques of the drive motor and of the steering motor possible turning centers. 6. The method according to claim 4, characterized in that the amount of turning centers allowed depending on the Time or energy optimized speeds and moments of the Drive motor and the steering motor possible turning centers. 7. The method according to claim 4 to 6, characterized in that by setting the appropriate moments and speeds the drive motors and / or the steering motors from the outside acting forces or moments are compensated and the on driving and steering torques are adapted accordingly. 8. The method according to claim 7 characterized in that  the external forces and moments Force, or moment sensors, by moment sensors in the Wheels or by detecting the current at the drive and / or steering motors are detected. 9. wheel modules according to claim 1, 2 and 3 with and without electronics cal coupling according to claim 4, 5 and 6 characterized in that so that all kinds of vehicles can be steered and driven nen. 10. Wheel modules according to claim 1, 2 and 3 with and without electronics cal coupling according to claim 4, 5 and 6 characterized in that thus vehicles in the handicapped and health care, like mobi le transport robots such as mobile transport robots for meals, Medicines, feces, etc., mobile robots with manipulations facility for collection / delivery services, patient guidance, etc. Roll chairs, stretchers, controlled or driven beds become. 11. Wheel modules according to claim 1, 2 and 3 with and without electronics cal coupling according to claim 4, 5 and 6 characterized in that so that cleaning and cleaning machines are steered or driven become. 12. Wheel modules according to claim 1, 2 and 3 with and without electronics cal coupling according to claim 4, 5 and 6 characterized in that so that mobile tripods for film cameras can be steered or driven become.   13. Wheel modules according to claim 1, 2 and 3 with and without electronics cal coupling according to claim 4, 5 and 6 characterized in that thus shopping carts in sales shops and their parking spaces are steered or driven. 14. Wheel modules according to claim 1, 2 and 3 with and without electronics cal coupling according to claim 4, 5 and 6 characterized in that with it, brief transport vehicles in offices and administrative buildings are steered or driven. 15. Wheel modules according to claim. 1, 2 and 3 with and without electronics cal coupling according to claim 4, 5 and 6 characterized in that so that earth and snow clearing vehicles are steered or driven be, the clearing device solely by the one another independently predefinable translation or rotation of the vehicle is moved. 16. Wheel modules according to claim 1, 2 and 3 with and without electronics cal coupling according to claim 4, 5 and 6 characterized in that with it vehicles for climbing large inclines or for climbing bring great pushing forces with simultaneous rotation and Translation can be moved.