METHOD AND ARRANGEMENT FOR SIMULATING THE MOTION OF A ROTATABLE BODY

Abstract

A method and an arrangement for simulating the motion of a rotatable body in a simulation computer using a brake test bench, which has an engine, a real rotatable body representing the simulated rotatable body and a brake. The method includes the method steps of: specifying a target speed, applying this target speed to the engine, rotating the real rotatable body, specifying a braking value, controlling the brake on the basis of the specified braking value, measuring the actual torque and the actual speed of the real rotatable body, determining whether the actual speed exceeds a predetermined limit speed, and simulating the motion of the rotatable body on the basis of a torque of the simulated rotatable body. In this way, a possibility for simulating the motion of a rotatable body is provided, which provides at least approximately correct results even for low speeds of the rotatable body.

Claims

1. A method for simulating a motion of a rotatable body in a simulation computer using a brake test bench that comprises an engine, a real rotatable body representing the simulated rotatable body and a brake for braking the real rotatable body, the method comprising: specifying a target speed using the simulation computer; applying this target speed to the engine; rotating the real rotatable body via the engine pressurized with the target speed; specifying a braking value using the simulation computer; controlling the brake acting on the real rotatable body on the basis of the specified braking value; measuring the actual torque and the actual speed of the real rotatable body; determining whether the actual speed exceeds a predetermined limit speed, and simulating the motion of the rotatable body in the simulation computer on the basis of a torque of the simulated rotatable body corresponding to the measured actual torque of the real rotatable body if the actual speed exceeds the predetermined limit speed, or simulating the motion of the rotatable body in the simulation computer on the basis of a determined value for the torque of the simulated rotatable body if the actual speed does not exceed the predetermined limit speed.

2. The method according to claim 1, wherein the value for the torque of the simulated rotatable body is determined on the basis of actual torques previously measured as a function of the actual speed.

3. The method according to claim 2, wherein the value for the torque of the simulated rotatable body is determined by extrapolation of previously measured actual torques as a function of the actual speed.

4. The method according to claim 3, wherein the actual torques previously measured for the extrapolation as a function of the actual speed have only been measured after the actual speed has approximated the limit speed by a predetermined measure.

5. The method according to claim 3, wherein the extrapolation is carried out on the basis of a parameterizable friction model, the parameters of which are adapted to the actual torques previously measured as a function of the actual speed.

6. The method according to claim 1, further comprising: measuring the actual brake pressure of the brake acting on the real rotatable body; and determining the torque value of the simulated rotatable body, taking into account the measured actual torque and the measured actual brake pressure.

7. The method according to claim 6, wherein the determination of the value for the torque of the simulated rotatable body is carried out taking into account the measured actual torque and the measured actual brake pressure using a Kalman filter.

8. An arrangement for simulating a motion of a rotatable body the arrangement comprising: a brake test bench comprising a real rotatable body, an engine for rotating the real rotatable body, a brake which, to slow down the rotation of the real rotatable body, acts on the real rotatable body, a torque sensor for measuring the actual torque of the real rotatable body, and a speed sensor for measuring the actual speed of the real rotatable body; a simulation computer configured to specify a target speed for applying this target speed to the engine and a braking value for controlling the brake and to simulate the motion of the rotatable body in the simulation computer on the basis of a torque of the simulated rotatable body corresponding to an actual torque of the real rotatable body measured with the torque sensor if the actual speed measured with the tachometer exceeds a predetermined limit speed, or to simulate the motion of the rotatable body in the simulation computer on the basis of a determined value for the torque of the simulated rotatable body if the actual speed measured with the tachometer does not exceed the predetermined limit speed.

9. The arrangement according to claim 8, wherein the brake test bench further comprises a pressure sensor for measuring the actual brake pressure of the brake, which acts on the real rotatable body, and wherein the simulation computer is set up to determine the torque value of the simulated rotatable body, taking into account the measured actual torque and the measured actual brake pressure.

10. The arrangement according to claim 9, wherein the simulation computer is equipped with a Kalman filter for determining the value for the torque of the simulated rotatable body, taking into account the measured actual torque and the measured actual brake pressure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0024] FIG. 1 shows schematically, an arrangement for simulating the motion of a rotatable body according to an embodiment of the invention; and

[0025] FIG. 2 shows schematically, the sequence of a method for operating the arrangement from FIG. 1.

DETAILED DESCRIPTION

[0026] FIG. 1 schematically shows an arrangement for simulating the motion of a rotatable body 3 with a brake test bench 1 and a simulation computer 2 according to an embodiment of the invention. In the present case, the rotatable body 3 is a wheel that represents a wheel of an engine vehicle to be simulated but does not have to be designed exactly like the wheel to be simulated. In the present case, the aim is to test the dynamics of this wheel during braking by simulation.

[0027] For this purpose, the brake test bench 1 has, in addition to the real rotatable body 3, an engine 4 for rotating the real rotatable body 3 and a brake 5, which, to slow down the rotation of the real rotatable body 3, can act on the real rotatable body 3. To rotate the real rotatable body 3, it is coupled to the engine 4 via a drive shaft 10. The brake 5 is controlled by means of a brake force generator 6. In addition, the brake test bench 1 is equipped with a torque sensor 7 for measuring the actual torque of the real rotatable body 3 and a speed sensor 8 for measuring the actual speed of the real rotatable body 3.

[0028] The simulation computer 2 is set up to specify a target speed for applying this target speed to the engine 4 and, as indicated by a corresponding arrow, to supply it to the engine 4. In addition, the simulation computer 2 is set up to specify a brake force for controlling the brake 5 as the braking value and, as also indicated with a corresponding arrow, supply it to the brake force generator 6.

[0029] Specifically, the method for simulating the motion of the rotatable body 3 in the simulation computer 2 using the brake test bench described above is as follows. This is shown schematically in FIG. 2:

[0030] In a first step S1, a target speed is specified using the simulation computer 2. With this target speed, the engine 4 is pressurized in step S2. In step S3, a rotation of the real rotatable body 3 takes place. Furthermore, in step S4, a braking value is specified by means of the simulation computer 2, so that in step S5, a control of the brake 5 acting on the real rotatable body 3 is carried out on the basis of the specified braking value. For this purpose, the brake force generator 6 acting on the brake 5 is controlled accordingly by the simulation computer 2.

[0031] In step S6, the actual torque and the actual speed of the real rotatable body 3 are measured as well as the actual brake pressure of the brake acting on the real rotatable body 3. The actual torque and the actual speed of the real rotatable body 3 are supplied to the simulation computer 2, as indicated by corresponding arrows in FIG. 1. In step S7, the simulation computer 2 determines whether the actual speed exceeds a predetermined limit speed. In the present case, that limit speed is fixed in such a way that, although it has only a low value, it is different from zero.

[0032] In step S8, the motion of the rotatable body 3 in the simulation computer 2 is then simulated on the basis of a torque of the simulated rotatable body, which corresponds to the measured actual torque of the real rotatable body 3, if the actual speed, designated in FIG. 2 with D.sub.i, exceeds the predetermined limit speed, designated in FIG. 2 with D.sub.G. Alternatively, in step S9, the motion of the rotatable body is simulated in the simulation computer on the basis of a determined value for the torque of the simulated rotatable body, if the actual speed does not exceed the predetermined limit speed.

[0033] Specifically, the value for the torque of the simulated rotatable body is determined by extrapolating actual torques previously measured as a function of the actual speed. However, the actual torques previously measured for extrapolation as a function of the actual speed have only been measured after the actual speed has approached the limit speed by a predetermined measure. In this way, it can be ensured that, in order to determine the torque value of the simulated rotatable body, such measured actual torques are used, which belong to actual speeds that are not too far from the limit speed, so that mostly realistic values for the torque of the simulated rotatable body are obtained. The extrapolation is carried out here on the basis of a parameterizable friction model, the parameters of which are adapted to the actual torques previously measured as a function of the actual speed.

[0034] As explained above, the actual brake pressure of the brake 5 acting on the real rotatable body 3 was also measured in step S6. Although it would not be necessary in principle to take this value into account, in the present case the value for the torque of the simulated rotatable body is determined taking into account the measured actual torque and the measured actual brake pressure. This determination is done using a Kalman filter, which further improves the approximation to a realistic value.

[0035] Overall, at low speeds, instead of the measured brake force, a determined value is used, which is determined from a measurement or from several measurements that have previously been carried out at a sufficiently high speed. In this way, the problem of the rotatable body 3 stopping and incorrect values being delivered, which would lead to incorrect simulation results, is avoided.

[0036] In summary, the effect of the method described here is as follows: The rotatable body 3 of the brake test bench 1 rotates at a nominal speed. A braking torque applied by a real brake 5 acts on the rotatable body 3. As soon as a blockage of the rotatable body 3 turns the rotational speed to zero, although the target speed specifies a value other than zero, the measured torque of the brake 5 is also zero, and consequently, also the braking effect derived from the measured torque in the model. However, the torque determined by the approach described above provides a realistic torque even when the rotatable body 3 is blocked.

[0037] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.