Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Reexamination Certificate
2002-03-05
2004-10-12
Martin, David (Department: 2837)
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
C318S564000, C318S565000, C318S639000, C318S798000, C318S806000, C361S023000, C388S907500, C388S909000, C180S404000, C180S443000
Reexamination Certificate
active
06803736
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a system for controlling a regulator in a motor vehicle and the use of this control system for an electronic steering system, a sway stabilization system, brake system, and a steering wheel simulator.
In a prior art control system, a parallel model forms an estimated parameter for the instantaneous value originating from the setpoint by simulating the control loop and affects the transmission properties of a gearshift, which in turn determines the gearshift parameter from the estimated parameter. Safety aspects are not affected by the model-assisted estimation of the prior art control system.
The purpose of electric-motor regulators in motor vehicles is often to set positions with high speed and accuracy. Despite robust controls, the desired position can often not be reached within the required time. This is determined on the one hand by the characteristics of the regulator, such as its inertia and PDI properties, and on the other hand by the servomotor used, for example its counter-torque.
As an example, an electronic steering system may be mentioned. Safety aspects play a large role in an electronic steering system. Decisions have to be made in the safety design for evaluating the regulated parameters (positional accuracy and speed of the electric motor used as the steering regulator), and as the case may be, turning off the electronic steering system has to be initiated. One problem of the safety design to be set up for this consists of finding the proper criterion for turning off the electronic steering system. Simple interpretation of the signals from the sensors in the electronic steering system does not lead to the target; instead, the dynamic behavior of the system has to be taken into consideration.
It is the purpose of the instant invention to describe a control system of th type so that it can evaluate the drive signals necessary for the safety monitoring of an electric-motor regulator (reach the setpoint position in a definite time), and can make decisions for turning it off.
SUMMARY OF THE INVENTION
As an important aspect, the control system pursuant to the invention contains a model-assisted monitoring device that provides the necessary information for being able to evaluate the suitability of the correction with reference to a model of the servomotor.
For this purpose, the monitoring device has a load torque estimator and models for the servomotor and for the control section, and an error interpreter device, which undertakes steps for the safety of the units adjusted by the regulator and of the vehicle, independently of the theoretical values determined by the models and of the load torque estimate.
The result of the load torque estimation serves the error interpreter device for deciding on the validity of the actual current and position differential signals determined by the modeling.
The model of the servomotor determines the load torque actually applied by the motor. Thereupon, the load torque to be applied by the servomotor is estimated as a function of the operating condition, and is compared with the instantaneous load torque determined with reference to the model.
With knowledge of the load, the parameters of the instantaneous current and position of the servo drive can then be calculated through the control model of the control section, which in turn are again compared with the measured values and checked for plausibility by the error interpreter device within established limits. A safety system designed using the control system and monitoring device pursuant to the invention makes the described plausibility monitoring the basis for deciding whether the system is turned off or not.
Using the model of the current control circuit and the model of the position control circuit, estimated condition parameters are set up for the instantaneous current and instantaneous position values.
The estimated values are fed to the error interpreter device in order to control the safety system, i.e., for example, to initiate the shutdown of the regulator mechanism.
In the electronic steering system chosen as an example of embodiment, the theoretical value of the load torque estimated with the load torque estimator is accordingly determined or calculated with the assistance of characteristics and knowledge of the possible load states. If the vehicle is also equipped with power steering, the (relatively simple) characteristic line or characteristic field of the servo steering is also stored in the load torque estimator. Depending on the steering angle, measured by an angle sensor, and/or on the steering rate, an estimated value of the load torque is determined from the field of characteristic lines. By comparing the actually measured load with the theoretically possible load, it can be determined whether the steering servomotor is operating in orderly fashion or whether extraordinary external conditions or a defect of the servomotor makes it necessary to turn off the system.
In the example of the servomotor for an electronic steering system for single-wheel steering or for steering of two wheels connected to one another through a tie rod, it can thus be differentiated whether the servomotor is in the fully operable working range, or whether a malfunction may make a shutdown necessary.
An important benefit of using the control system pursuant to the invention for an electronic steering system lies in the fact that only with the assistance of angle sensors and a current sensor—without a torque sensor—it can be judged whether the control system is operating in orderly fashion or whether a shutdown of the system is necessary because of a broken shaft, worn bearing, broken gear, increased frictional forces from wear, and the like, or because of extraordinary external conditions (for example, steering into the curbing).
It should be emphasized here explicitly that the principles pursuant to the invention can be used not only for electronic steering systems, but also in motor vehicles for other regulators using an electric servomotor, for example for electronic brake systems, sway stabilizers, steering wheel simulators for steer-by-wire applications, and automatic suspension- and/or level-control systems, in which safety aspects likewise play an important role.
The control system pursuant to the invention is described generally in detail below, and by way of example, its use for an electronic steering system used for an electric-motor steering regulator, with reference to the drawing.
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Hommel Mathias
Kraemer Wolfgang
Baker & Daniels
Martin David
Martin Edgardo San
Robert & Bosch GmbH
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