Method and control unit for reducing the lateral forces acting on a motorcycle

Abstract

Method for reducing the forces acting on a motorcycle during an unstable cornering maneuver (3), characterized by the following steps: - monitoring the driving situation with regard to an unstable condition in which the rear wheel of the motorcycle slips laterally during a cornering maneuver, and - limiting the decrease in engine torque (7) when the rider reduces the engine torque (6) in such a situation, by changing the spring / damper characteristic of a suspension of the drive wheel.

Description

State of the art The invention relates to a method for reducing the lateral forces acting on a motorcycle according to the preamble of claim 1, and to a control unit for carrying out such a method according to the preamble of claim 6. From DE 10 2005 028 995 A1 a method for controlling vehicle dynamics for motorized single-track vehicles is known, which evaluates camera image sequences with regard to the lean angle p and / or the pitch angle of the vehicle to the road. When cornering a motorcycle, the tires' grip limit can be exceeded at excessive speed. If this happens, the rear wheel begins to slide towards the outside of the curve, with a significant increase in slippage. If the rider reduces the throttle in such a situation, the slippage decreases, and the rear wheel suddenly regains traction. This causes the motorcycle to stand upright, the rear shock absorber fully compresses and rebounds, and the rider is ejected from the seat. This type of riding situation is also known as a "highside." Fig. 1 shows the trajectory of a motorcycle during a cornering maneuver, in one case remaining stable through the curve and in the other experiencing a highside. The stable cornering maneuver is indicated by reference numeral 2, and the unstable cornering maneuver with a highside is indicated by reference numeral 3. In a highside situation, the motorcycle initially moves along trajectory 2, from left to right, until point T1. At this point, the maximum transmissible lateral grip of the rear tire is exceeded. This causes the rear wheel to slide outwards. The motorcycle then moves along line 3 towards the outside of the curve. At point T2, the rider intuitively reduces the throttle to prevent further slippage of the rear wheel and a potential crash. This allows the rear wheel to regain traction. Between points T2 and T3, the motorcycle rights itself due to the regained lateral grip. The rear shock absorber compresses and rebounds at position T3, catapulting the rider from the seat. If the rider has not been thrown, the rear wheel returns to its original position between points T3 and T4, allowing the ride to continue.However, such a driving situation is usually no longer controllable for inexperienced drivers. Disclosure of the invention It is therefore the object of the present invention to provide a method and a device with which the forces acting on the motorcycle and the rider in such a situation can be reduced. This problem is solved according to the invention by the features specified in claim 1 and claim 6. Further embodiments of the invention are the subject of dependent claims. According to the invention, it is proposed to monitor the riding situation with regard to an unstable condition in which the rear wheel slips laterally during cornering. Such an unstable riding condition always occurs in the first phase of a highside and thus indicates the danger of a highside. According to the invention, the reduction in engine torque is limited when the rider reduces engine torque in such a situation. It has been shown that the dynamics of a highside depend primarily on how quickly the rider reduces the throttle after recognizing the critical situation. If the permissible reduction in engine torque is automatically limited, the forces acting on the motorcycle and the rider can be significantly reduced. The aforementioned unstable state is preferably detected by evaluating one or more of the following parameters, in particular the slip angle at the rear wheel, the steering angle, the lean angle, the accelerations, the wheel slip at the rear wheel, the vehicle speed, and / or the gradient of one of the aforementioned parameters. An unstable state is detected if the behavior of one or more of the parameters corresponds, for example, to a specific, predetermined pattern, or if at least one of the parameters exceeds a predetermined threshold. According to a preferred embodiment, the wheel slip gradient and / or the slip angle gradient at the rear wheel is monitored. If the gradient in question exceeds, for example, a certain threshold and subsequently reaches zero during the maneuver (i.e., the quantity under consideration reaches a maximum), the risk of a highside is detected and the decrease in engine torque is limited. The maximum value to which the decrease in engine torque is limited is preferably dimensioned such that the slip angle at the rear wheel, the steering angle, and / or the rear wheel slip do not swing in the opposite direction. That is, if the monitored parameter is in a positive range during the initial phase of a highside, it should not enter a negative range, and vice versa. According to a particular embodiment of the invention, the spring and / or damper characteristics of a rear wheel suspension can be automatically changed after an unstable condition has been detected. Preferably, the spring / damper characteristics are changed at least such that the suspension rebounds more slowly. The maximum value to which the reduction in engine torque is limited can be variable and may depend on one or more of the following factors: the angle of the rear wheel slip, the steering angle, the lean angle, the accelerations, the wheel slip, the vehicle speed, and / or the gradient of any of these factors. The maximum value can thus be adapted to different situations. To detect the risk of a highside, suitable sensors are preferably provided that measure one or more of the aforementioned parameters. A control unit with a corresponding algorithm evaluates the sensor signals and limits the reduction in engine torque, e.g., by controlling the injection system or the throttle valve, when the risk of a highside is detected. The invention is explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 a road surface with the trajectory of a motorcycle during a stable cornering maneuver and a highside; Fig. 2a the engine torque curve during a highside with and without limiting the permissible reduction in engine torque; Fig. 2b the rear wheel slip curve with and without limiting the reduction in engine torque; and Fig. 2c the rear wheel slip angle curve with and without limiting the reduction in engine torque. For an explanation of Fig. 1, please refer to the introductory description. Fig. 2a shows the engine torque curve 6 during a highside while cornering. In the example shown, the rider steadily increases the engine torque from time T to a maximum value. The rear wheel loses its traction and slides sideways. As already described with reference to Fig. 1, the rider abruptly reduces the engine torque from time T2 to avoid a crash. A steep gradient can be seen in the characteristic curve 6. To dampen the subsequent compression of the rear wheel and reduce the forces acting on the motorcycle and rider, the decrease in engine torque is limited to a specific value. This is shown as dashed line 7. As can be seen, line 7 shows a smaller gradient than the engine torque applied by the rider. Figures 2b and 2c show the corresponding curves of the wheel slip λ and the slip angle β at the rear wheel. In the phase between times T1 and T2, both the wheel slip (curve 5) and the slip angle (curve 4) at the rear wheel increase steadily until a maximum is reached at approximately time T2. At this point, the rider instinctively reduces the throttle, and both the wheel slip λ and the slip angle β decrease sharply. As can be seen, the curve reverses so drastically that both the wheel slip λ and the slip angle β assume negative values. If, on the other hand, the engine torque is automatically limited (see characteristic curve 7), the decrease in wheel slip λ and slip angle β is less steep. Both values ​​remain in the positive range. As a result, the dynamic processes on the motorcycle are significantly slower, and in the best-case scenario, the rider is not thrown from the motorcycle.

Claims

Method for reducing the forces acting on a motorcycle during an unstable cornering maneuver (3), characterized by the following steps: - monitoring the driving situation with regard to an unstable condition in which the rear wheel of the motorcycle slips laterally during a cornering maneuver, and - limiting the decrease in engine torque (7) when the rider reduces the engine torque (6) in such a situation by changing the spring / damper characteristic of a suspension of the drive wheel. Method according to claim 1, characterized in that an unstable state is detected by evaluating one or more of the following quantities: slip angle (β) at the rear wheel, steering angle, lean angle, acceleration, wheel slip at the rear wheel, vehicle speed and / or the gradient of one of the aforementioned quantities. Method according to claim 1 or 2, characterized in that the decrease of the motor torque (7) is limited to a maximum value which is dimensioned such that the slip angle (β), the steering angle and / or the wheel slip (λ) at the rear wheel does not enter a negative value range. Method according to one of the preceding claims, characterized in that the wheel slip (λ) and / or the slip angle gradient (β) at the rear wheel are monitored and, if the gradient exceeds a certain threshold value and subsequently reaches zero, an unstable condition is detected and the decrease in engine torque (7) is limited. Method according to one of the preceding claims, characterized in that the maximum value to which the decrease of the motor torque (7) is limited depends on one or more of the following quantities: the magnitude of the slip angle (β), the steering angle, the tilt angle, an acceleration, the wheel slip (λ), the vehicle speed and / or the magnitude of the gradient of one of the aforementioned quantities. Control unit, comprising means for carrying out one of the aforementioned procedures.

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