DE19948486A1 - Device for positioning of body has facility whereby body is driven by one or more wheels and steering angle is adjustable via driving torque which is provided by motor by means of corresponding control - Google Patents

Abstract

The body is driven by one or more wheels and the steering angle is adjustable via the driving torque. The driving torque of the wheel is provided by a motor by means of a corresponding control, and with a constant steering angle locking takes place. Two wheels may be assembled to form a suspension module, and with each wheel driven on its own. Two wheels may be assembled to form an axle and with a mechanical coupling in the form of track rod. In this case the steering angle is set by the driving torques of each wheel synchronized with each other.

Description

Steering by means of the drive (under driving is a movement with constant speed, a deceleration or a Acceleration understood) for non-lane-bound vehicles.

field of use

According to the preamble of claim 1, the invention relates to a steering principle that allows

• - manipulate the steering angle of a wheel
• - while ensuring the drive of the vehicle.

State of the art

In vehicle technology as well as in the development of aircraft chassis steering and drive mechanisms are implemented based on the separation of functions Steering and driving are based. That is why today's steerable and driven axles need several constructive mechanisms for the transmission of the drive torque as well also for the steering angle adjustment of the wheel [1]. For example, at Passenger cars with front-wheel drive and front steerable axle the two front wheels via a mechanical steering linkage inclined relative to the vehicle. Also are for the drive shafts with compensating joints between the gearbox and the wheels.  

Mechanisms are used in the development of holonomic and non-holonomic mobile robots used, which are based on a combination of steering and driving [5]. In doing so non-steerable wheels driven by motors at different speeds, from which there is a rotational movement about the vertical axis. Steerable wheels are additional to the drive units actuators and mechanical elements for the adjustment of the Steering angle required.

literature

[1] Reimpell, J .: Chassis technology: wheel suspensions, rigid axles, independent wheel suspensions, advantages, disadvantages, tire influence, kinematics, elastokinematics, individual parts, materials, costs. 2nd, revised. u. adult Aufl. Würzburg: Vogel, 1988.
[2] Pflug, H.-Ch .: Influence of intelligent additional rear axle steering on the driving behavior of commercial vehicles. 3rd Stuttgart Symposium Automotive and Internal Combustion Engines, Conference proceedings, Stuttgart: Expert Verlag, 1999.
[3] Rear rumble - Mercedes

814

with all-wheel steering, truck Omnibus, issue 10.
[4] Khatib, O .: Force Strategies for Cooperative Tasks in Multiple Mobile Manipulation Systems. Int. Symp. On Robotics Research, Munich, 1995.
[5] Kortenkamp, D .: Artificial intelligence and mobile robot, case studies of successful robot systems, Menlo Park, Calif .: AAAI Press, 1998.

Disadvantages of the prior art

The current steering and drive concepts have several disadvantages:

When separating the functions of steering and driving, as is the case with today's motor vehicles State of the art, two mechanisms must be combined in one construction. The resulting space problems always lead to a compromise on the kinematic limits of the system, such as the maximum to be set Head angle. In addition, the steering angle increases as the steering angle increases Usually used mechanical coupling of the right and left wheel increasing cross-slip. This results in increased tire wear and more As the steering angle increases, the driving condition moves more and more into the Border area.

The disadvantages described can be avoided by replacing autonomous steered wheels become. Actuators in conjunction with sensors and a control take over Function of the steering linkage, via which a desired steering angle can be set. Such a steering principle is very expensive due to the higher number of parts and also requires utility power to be supplied.

The rolling motion and the steering angle of the wheel are kinematic and dynamic coupled with each other, which must be considered with driven and steered axles. For this reason, the driving and steering torque on the wheel must match when driving maneuvers be coordinated so that the slip values do not exceed critical limits. A necessary one Coordination of the two torques when using actuators for the Steering movement requires an elaborate regulation, which results in great overall costs surrender.  

Presentation and advantages of the invention

The invention is based on the coupling of the drive and the steering movement of an autonomously steered wheel. The turning when steering is not achieved via an actuator or a linkage, but is influenced by the drive torque. A lever arm between the steering axle and the force in the wheel contact surface, which results from the drive, creates a torque around the vertical axis (see Figure 1). A change in the steering angle of the wheel can thus be achieved by regulating the drive.

In the steady state, i.e. H. at a constant steering angle, using a Clamping device held the rotation of the wheel relative to the body. This For this, the device must have a continuous, defined braking torque about the axis of rotation can generate. This additional mechanism is used during start-up or prevents unwanted inclination of the wheel during braking maneuvers.

Such a device can be dispensed with if two individually driven wheels are combined to form a module (see Figure 2). The steering angle can then be adjusted by metering the drive torques of both motors.

The following advantages result with regard to the aforementioned disadvantages of conventional systems:

• - By using the drive torque to turn the wheel around the Vertical axis can be dispensed with a steering linkage, which is constructive Free space.
• - In principle, can be on a complex actuator (electric motor with gear) for the steering angle manipulation, which results in a simple Overall construction results. Because of the existing drive unit for propulsion are also power supplies with large power transmission and regulations unnecessary for additional actuators.
• - The principle, in comparison to mechanisms as they are state of the art, the reduction of slip values during steering maneuvers because of the rolling movement of the wheel is kinematically / dynamically connected to the steering movement. The enlargement of the Longitudinal slip, as in independent steering angle and Drive control is not caused by this principle.

In the application initially sought, the drive takes place via regulated electrical Wheel hub motors. They are already developed or available in various designs (see eg literature [1. .5] before) and therefore not the subject of this application. Optionally, a brake can be integrated to increase the decelerating torque. By using such units, autonomous wheel modules can be created that are suitable for the desired steering kinematics of the entire vehicle no longer via linkage are interconnected.  

example Description of exemplary embodiments

The basic idea of the invention was already at the beginning of the previous section described. Various modifications and exemplary embodiments are now intended here to be named:

Because the principle presented is driving and steering an autonomous wheel positioning tasks or drive tasks can be derived (e.g. in the Vehicle technology or in the design of platforms for mobile robots).

By appropriately impressing the wheel drive torque and the interaction with the Locking device can adjust the steering angle. Unless you have a vehicle with such Wheel suspensions can move according to the three degrees of freedom in the Level. Such a car is characterized by an extreme Maneuverability.

The number of wheel modules on the vehicle is not limited; In principle, any number of such units can be mounted on the structure in order to increase the load-bearing capacity. Two wheels can be connected to each other by means of a steering linkage, so that a device for generating a braking torque can be dispensed with (see Figure 7).

Variants are also possible in which the wheel suspension manipulates the steering angle takes over without driving the vehicle. The actual jacking can take place over a conventionally driven rigid axis. Only when the environmental conditions requiring four-wheel drive would also drive the steerable wheels.

As a further exemplary embodiment, a wheel steering system constructed according to the principle presented can be fixed in the room (see Figure 3). Such a construction enables the positioning of a body mounted on the suspension via the drive torques and the set steering angle.

The one driven wheel per drive module for stationary steering angle specifications necessary clamping device can be designed as a positive and non-positive connection. Such systems are easy to manufacture or available as purchased parts.

To increase the driving force, several driven wheels can also be combined (see Fig . 2). In this case, locking can be dispensed with if the moments are coordinated accordingly.

With regard to the structural design, conventional steerable wheel suspensions, such as those used in vehicle technology, can be used (see Figure 6). The overall structure must be extended by a locking device and an associated torque control must be available. The exact dosage of the drive can, for. B. via an electric motor or a hydraulic motor.

Claims (7)

1. Device for positioning a body according to position and orientation in the plane, characterized in that the body is driven by one or more wheels, and the steering angle is adjusted via the drive torque ( Figure 1). 2. Device according to claim 1, characterized in that the drive torque of the wheel is predetermined by a motor by means of a corresponding control and the locking takes place at a constant steering angle ( Figure 1). 3. Apparatus according to claim 1, characterized in that two wheels are combined to form a suspension module and each wheel is driven separately (see Figure 2). 4. The device according to claim 1, characterized in that two wheels are combined to form an axis and a mechanical coupling by means of a tie rod is present ( Figure 7). The steering angles are set by coordinated drive torques of the two wheels. 5. Device according to one of the preceding claims, characterized in that this device is used for positioning in one plane in manufacture, in vehicle technology and in the development of mobile robots ( Figure 2, Figure 3). 6. Device according to one of the preceding claims, characterized in that the above-mentioned principles are also carried out on (below, at) arbitrarily oriented levels or the working principle is reversed so that the wheel module is stationary and the plane is moved by the wheel ( Image 4). 7. Device according to one of the preceding claims, characterized in that the body to be positioned is guided flat and the drive is carried out via the working principle ( Figure 5).