DAMPER

Field of the invention

The present invention relates to the field of steering dampers for motorcycles and the control of its damping. In particular, the invention relates to a method for controlling damping of a steering damper and a steering damper. Furthermore, the invention relates to a method and device for identifying wobble during operation of motorcycle.

Background of the invention

A steering damper for motorcycles is mounted between a rotating handlebar and its fixed frame or chassis in order to damp shocks and violent movements that propagate from the front wheel to the handlebar. When the steering damper is used on a motorcycle, the steering damper is also used to solve the problem of wobbling that may occur in a motorcycle at high speeds. Wobbling refers to the front wheel on the motorcycle beginning to oscillate about the steering axis with increasing amplitude.

Thus, many different types of steering dampers exist which take into account various problems. For example, one problem relates to separate desired steering movements from undesired shocks caused by unevenness of the ground in a steering damper. In order to not create a delay in the steering movement when the driver turns the handlebar, it is desirable that this desired rotational movement is undamped. At the same time undesired rotational movements caused by shocks from the ground should be damped as much as possible to minimize the risk of the handlebar being stricken from the hands of the driver. Thus, it is desirable to provide a steering damper that actively adapts the damping on basis of the cause of the movement. In EP1248013 a steering damper is disclosed that by means of electronics senses and controls the damping on the handlebar depending on whether the movement is caused by the driver or the ground. In addition to the problem mentioned above, the steering damper also needs to take into account the damping during various running states. At low vehicle speeds a low damping degree of the steering damping is desired, thereby an easily manoeuvrable handle is achieved. On the other hand, at a high vehicle speed a high damping degree is desired to thereby achieve a good steering stability. Thus, another problem of steering dampers is to regulate the damping degree during operation, i.e. driving, of the motorcycle. In US 2009/0008197 a steering damping method and a steering device is disclosed which controls the steering device in response to the speed of the motorcycle and the acceleration thereof.

Similarly, in EP 1561 677 a steering damper is disclosed wherein the damping force is variably controlled in response to the motorcycle speed. The damping force is fixed to a minimum value when the speed is equal or below a first predetermined value and is fixed to a maximum value when the speed is equal or above a second predetermined value.

Furthermore, in EP 1247729 a control device may generate a damping force at the steering damper only when an acceleration detected by an acceleration speed sensor exceeds a threshold value. In addition, when the fact that vehicle body speed detected by the vehicle body speed sensor exceeds a threshold value is applied as a weighting condition for control, a change in occurrence of acceleration speed caused by a vehicle body speed can be corrected.

The continued development of motorcycles continuously increases the demand for more advanced control systems including steering dampers having a more accurate control of the damping. In order to meet such demands and to also increase the degree of safety during the operation of the motorcycle, more complex control systems may be provided and preferably adapted to take into account unwanted wobble. However, a drawback of providing more complex control systems is that a large number of steering damping situations and parameters need to be considered which not always reduces unwanted wobble.

Summary of the invention An object of the present invention is to provide a method for identification of wobble and a device for detection of wobble during the operation of a motorcycle.

Another object of the present invention is to provide a method for controlling damping of a steering damper device and a steering damper device.

This and other objects of the present invention are achieved by a method for identification of wobble, a method for controlling damping of a steering damper, a wobble detection device and a steering damper device having the features as defined by the independent claim. Certain

embodiments are characterized by the independent claims.

According to a first aspect of the present invention, there is provided a method for identification of wobble during operation of a motorcycle having a chassis and a handlebar, said method comprising the steps of:

- monitoring motion of the handlebar;

- deriving a value of at least two relative motion parameters from the monitored motion, said relative motion parameters representing a movement of the handlebar relative to said chassis, and wherein one of the two relative motion parameters is based on a frequency of a reciprocal movement of the handlebar, and the other is based on a position of the handlebar; and

- verifying correspondence between the derived values and corresponding predetermined values, thereby identifying wobble.

According to a second aspect of the present invention, there is provided method for controlling damping of a steering damper arranged between a handlebar and a chassis of a motorcycle during operation thereof, the method comprising the steps:

- repeatedly applying a damping signal in order to control said damping of said steering damper; and

- adjusting, when receiving a signal indicating wobble, said damping signal in order to increase the damping of said steering damper, thereby at least mitigating said wobble.

According to a third aspect of the present invention, there is provided a wobble detecting device for detection of wobble during operation of a motorcycle having a chassis and a handlebar, said wobble detecting device being adapted to

monitor motion of the handlebar;

derive a value of at least two relative motion parameters from the monitored motion, said relative motion parameters representing a movement of the handlebar relative to said chassis, and wherein one of the two relative motion parameters is based on a frequency of a reciprocal movement of the handlebar, and the other is based on a position of the handlebar; and

verify correspondence between the derived values and corresponding predetermined values, thereby detecting wobble.

According to a fourth aspect of the present invention, there is provided steering damper for controlling damping during operation of a motorcycle having a chassis and a handlebar, the steering damper being adapted to repeatedly apply a damping signal in order to control said damping of said steering damper; and

to adjust, when a signal indicating wobble is received, said damping signal in order to increase the damping of said steering damper, thereby at least mitigating said wobble.

According to a fifth aspect of the present invention, there is provided steering damping system for controlling damping of a handlebar relative to a chassis of a motorcycle, the steering damping system comprising

a sensor for monitoring motion of the handlebar, said sensor being adapted to provide a sensor signal representing said motion;

a steering damper for damping said handlebar relative to said chassis, said steering damper being adapted to damp said handlebar in response to a damping signal; and

a controller adapted to repeatedly apply a damping signal to said steering damper for controlling said steering damper, said controller being further adapted to

derive a value of at least two relative motion parameter from the sensor signal, said relative motion parameter representing a relative movement of the handlebar relative to said chassis, and wherein one of the two relative motion parameters is based on a frequency of a reciprocal movement of the handlebar, and the other is based on a position of the handlebar, and to

verify correspondence between the derived values and corresponding predetermined values thereby identifying wobble, and wherein said

controller being further adapted to, when said controller has verified said correspondence, adjust said damping signal in order to increase the damping of said steering damper.

According to a sixth aspect of the present invention, there is provided computer program product comprising computer-executable components for causing a device to perform the steps recited in any one of claims 1 to 6 when the computer-executable components are run on a processing unit included in the device.

The present invention is based on the insight that wobble may be identified by monitoring the motion of the handlebar. In particular, by using the frequency based parameter and the position based parameter, an accurate identification of wobble is achieved. Thus, the motion of the handlebar is identified as wobble if the both the frequency condition and the position condition are fulfilled. Both the frequency based parameter and the position based parameter need to be considered for determining the energy of the wobble which has been supplied to the system, i.e. to the motorcycle. For example, the handlebar may have a non-wobble vibration which has a frequency which fulfil the frequency condition, but where the position condition is not fulfilled, and vice verse.

It is understood that the handlebar is connected to the chassis via a steering axis and wherein the handlebar is rotatable, i.e. steerable, about the steering axis. Thus, the relative motion of the handlebar is relative the steering axis of the chassis, thereby the relative motion parameters represents a movement of the handlebar relative to the steering axis.

Consequently, the motion of the handlebar is monitored by registering values of the motion of the handlebar. Various motions detecting means may be used to monitor and register the motion. The registration of the values may be registered by using a potentiometer which registers relative position values representing a relative position of the handlebar relative to the chassis, or the steering axis, of the motorcycle. Values of a relative velocity of the handlebar, i.e. the velocity of the handlebar relative to the chassis, are determined by performing a differentiating process on the relative position values of the relative position, and if yet another differentiating process is performed on the velocity an acceleration value is determined, or vice versa, a integrating process may be performed on an acceleration to determine the velocity.

Furthermore, a peak-to-peak amplitude of the position based parameter may be obtained by measuring the distance between the two end positions, i.e. the position where the handlebar changes motion direction, of the moving handlebar. However, it is understood that other values of the position based parameter may be used to determine a wobble motion, e.g. other amplitude values. Thus, by registering the relative position of the handlebar, the distance, or angle, in which the handlebar moves, may be determined. Put differently, the difference, with respect to distance or angle, between the end positions of the movement of the handlebar during operation of the

motorcycle may be determined. It is understood that the frequency is derived from the two sets of values, i.e. the relative position and relative velocity values, by means of frequency analysis.

Alternatively, the motion may be monitored by registering other values of other relative motion parameters, such as accelerometers registering acceleration, gyros registering angular velocity, and angular measuring sensors for registering the angular motion relative to the chassis. It is understood that a relative motion parameter based on a position may be one of an acceleration parameter, a velocity parameter, or a position parameter of the relative motion the handlebar, i.e. relative to the chassis. It is also understood that, in combination with of various differentiating and/or integrating steps, the frequency of the moving handlebar may be derived from various parameter, such as position, velocity and acceleration. Furthermore, it is also understood that these parameters may be expressed in terms of angle or distance, i.e. the relative angle or relative distance of the motion of the handlebar relative to the chassis via the steering axis. A pressure sensor may also be used. In case of a linear steering damper having a cylinder and a piston, the piston is arranged to be linearly and reciprocally movable in the cylinder. Thus, the cylinder and the piston cooperate with each other such that the piston reciprocally moves in a compression stroke and a rebound stroke thereby achieving a linear motion. A pressure sensor may be arranged inside the cylinder, e.g. on the piston, which then registers pressure values during the motion of the piston which correspond to the motion velocity mentioned above. Furthermore, the pressure inside the cylinder, e.g. the oil pressure, is also registered which corresponds to the position of the handlebar. Also a peak-to-peak value may be determined from registering the pressure inside the cylinder.

It is also understood that although both conditions need to be fulfilled, the two conditions may be investigated consecutively or simultaneously.

In other words, the motion of the handlebar is defined as wobble if the derived values of both the frequency based parameter and the position based parameter are verified with the corresponding predetermined values. When a wobble is indentified, the damping degree can thereafter be adjusted for eliminating unwanted wobble and thus enabling an accurate damping degree of the steering damper. Consequently, when the motorcycle is subjected to wobble this unwanted state is instantaneously and accurately eliminated or at least mitigated.

Moreover, in order to clarify, the term "motion frequency" used herein refers to a frequency of the reciprocating motion of the handlebar. In other words, this reciprocating motion corresponds to the motion of which the piston reciprocally moves relative to the cylinder.

According to an embodiment of the present invention, said step of monitoring motion of the handlebar comprises a step of registering values of the motion of the handlebar, and wherein said step of deriving a value of at least two relative motion parameters from the monitored motion comprises deriving a value of at least two relative motion parameters from the registered values.

According to another embodiment of the present invention, said step of repeatedly applying a damping signal further comprises the step of - varying said damping signal in order to correspondingly vary said damping of said steering damper.

According to one embodiment of the present invention, said step of repeatedly applying a damping signal further comprises a step of

- maintaining the damping signal at a predetermined level in order to correspondingly maintain said damping at a predetermined level.

According to a further embodiment of the present invention, said signal indicating wobble is a signal which has identified wobble according to the method of identifying a wobble according to any of claim 1 or 2.

According to a further embodiment of the present invention, the wobble detecting device is adapted to register values of the motion of the handlebar, thereby deriving said values from the registered values.

According to one embodiment of the present invention, the steering damper is further adapted to vary said damping signal in order to

correspondingly vary said damping of said steering damper. Alternatively, according to another embodiment of the present invention, the steering damper is further arranged to maintain the damping signal at a predetermined level in order to correspondingly maintain said damping at a predetermined level.

In another embodiment, said signal indicating wobble is a signal which has identified wobble according to the method of identifying a wobble according to any of the claims 1 or 2.

According to one embodiment of the present invention, the steering damping system is further adapted to vary said damping signal in order to correspondingly vary said damping of said steering damper.

According to yet another embodiment of the present invention, the steering damping system is further arranged to maintain the damping signal at a predetermined level in order to correspondingly maintain said damping at a predetermined level.

Brief description of the drawings

In the following detailed description reference will be made to the accompanying drawings, of which Fig. 1 schematically shows general steps performed in accordance with an embodiment of the method according to the present invention.

Fig. 2 illustrates an embodiment of a steering damper of the present invention, wherein the steering damper is secured to a motorcycle at a first position.

Fig. 3 illustrates an embodiment of the steering damper of the present, wherein the steering damper is secured to the motorcycle at a second positon. Detailed description of the present invention

With reference to Fig. 1 , an embodiment of the method according to the present invention will be described. First, at step 1 , a first sensor registers a raw signal corresponding to the motion of a handlebar connected to a chassis of a motorcycle. Alternatively, in order to filter the signal of the first sensor, a second sensor may also be used which register a signal

corresponding to the motion of the chassis of the motorcycle, thereby the information which does not relate to motion of the handlebar is filtered. Thus, the raw signal is filtered by means of the signal related to the motion of the chassis of the motorcycle. If two sensors are used, the two sensors are preferably accelerometers. At step 3, the raw signal is passed through a bandpass filter to obtain a filtered signal, which is thereafter passed to two separate analyzing steps 5 and 1 1 . At step 5, the filtered signal is analyzed with regards to a motion frequency parameter, and at step 1 1 the filtered signal is analyzed with regards to a motion velocity parameter. Thus, at the step 5 and 1 1 , the filtered signal is analyzed to derive values related to the motion frequency parameter and motion velocity parameter, respectively.

In the case where the first sensor is an accelerometer, an integration step is performed on the filtered signal to derive a motion velocity value of a motion velocity parameter. Also, in the case where the first sensor is an accelerometer, it is understood that the second sensor is preferably also an accelerometer.

Furthermore, at step 13, the motion velocity value is further analyzed to obtain a velocity amplitude value of the motion velocity value. At step 7, the derived motion frequency value is compared with a predetermined frequency value corresponding to the wobble frequencies and, if a correspondence of the derived frequency value and the predetermined frequency value is verified, a first wobble signal indicative of wobble is obtained, i.e. the first wobble signal indicates that a wobble frequency condition is fulfilled. Similarly, at step 15, the velocity amplitude value of the derived motion velocity value is compared with a predetermined amplitude value corresponding to a wobble amplitude value. This predetermined velocity amplitude value is above a reference velocity amplitude value representing a lower limit. If the velocity amplitude value is below that reference value, i.e. the lower limit, the motion is defined as not being a wobble. Put in other words, if the velocity amplitude value is above the reference value the motions is defined as wobble, i.e. it is considered to represent a wobble motion. If a correspondence of the velocity amplitude value of the derived motion velocity value and the predetermined velocity amplitude value is verified, a second wobble signal indicative of wobble is obtained, i.e. the second wobble signal indicates that a wobble amplitude condition is fulfilled.

It is understood that the frequency of wobble may vary depending on different parameters, such as type and construction of motorcycle.

Furthermore, the predetermined value of the frequency may also be set at different values which thereby effect the "definition" of wobble.

At step 9, a wobble identification function receives signals from step 7 and 15. If the wobble identification function receives both the first wobble signal and the second wobble signal then wobble is identified. However, it is understood that each of the first and second wobble signal may individually identify a wobble, but both signals are required to ensure an accurate identification of wobble. For example, a vibration may fulfil the wobble frequency condition, but not the amplitude condition.

With reference to Fig. 2, which illustrates an embodiment of a steering damper of the present invention, wherein the steering damper is secured to a motorcycle at a first position. In fig. 2 a linear steering damper 21 is shown having a rod 22 which is operatively connected to a cylinder 23 by a piston (not shown). The rod 22 is fixed to the piston. The cylinder 23 and the piston are arranged such the rod and the cylinder move along the same axis, i.e. a linear steering damper 21 . The rod 22 is via a first attachment means 24a connected to a chassis 27 of a motorcycle 25, whereas the cylinder 23 is via a second attachment means 24b connected to a handlebar 26 of the motorcycle 25. A first sensor 29 is arranged at the second attachment means 24b. A second sensor 28 is arranged at a first end 22a of the rod, i.e. the end of the rod that is in contact with the attachment means 24. The first sensor 29 and the second sensors 28 are both accelerometers.

In case of a first and a second accelerometer, the first accelerometer 29 is adapted to monitor said motion of the handlebar and is adapted to provide a first signal. Furthermore, the steering damper 21 also comprises a second accelerometer 28 adapted to monitor the motion of chassis, and wherein the second accelerometer 28 is adapted to provide a second signal. Thereafter, the steering damper 21 is arranged to filter said first signal by means of the second signal in order to remove unwanted motion signals, thereby obtaining a signal representing the motion of said handlebar minus the motion of said chassis. Put differently, the first signal is filtered by means of a filter which uses information from the second signal. Thus, by comparing the first and the second signals, information is obtained about the relative motion of handlebar. The second accelerometer is thus a reference accelerometer adapted to provide a reference signal, i.e. the second signal, corresponding to a reference motion which both of the accelerometers monitors. By comparing these two signals with each other, a filtered signal is obtained which contains information related to only the motion of the handlebar.

With reference to Fig. 3, which illustrates an embodiment of a steering damper of the present invention, wherein the steering damper is secured to a motorcycle at a first position. Compared with the laterally mounted steering damper in Fig. 2, the steering damper in Fig. 3 is longitudinally mounted to the motorcycle 25. Similarly to the steering damper in Fig. 2, a linear steering damper 21 is shown having a rod 22 which is operatively connected to a cylinder 23 by a piston (not shown). The rod 22 is fixed to the piston. The cylinder 23 and the piston are arranged such the rod and the cylinder move along the same axis, i.e. a linear steering damper 21 . The rod 22 is via a first attachment means 24a connected to a chassis 27 of a motorcycle 25, whereas the cylinder 23 is via a second attachment means 24b connected to a handlebar 26 of the motorcycle 25. A first sensor 29 is arranged at the second attachment means 24b. A second sensor 28 is arranged at a first end 22a of the rod, i.e. the end of the rod that is in contact with the attachment means 24. The first sensor 29 and the second sensors 28 are both preferable accelerometers.

In the steering damper 21 in Fig. 2 and 3, a controller (not shown) is arranged, li is understood that the controller can be integrated with one of the sensors. The controller typically comprises one or more microprocessors or some other device with computing capabilities, e.g. a mircocontroller unit (MCU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a complex

programmable logic device (CPLD), etc., in order to control power supply and reloading of the battery set, while executing appropriate downloadable software stored in a suitable storage area, such as a RAM, a Flash memory or a hard disk. This controller receives signals from the sensors and processes these signals to obtain a control signal to the steering damper.

Although an exemplary embodiment of the present invention has been shown and described, it will be apparent to those persons having ordinary skill in the art that a number of changes and modifications, or alterations of the invention as described herein may be made. Thus, it is to be understood that the above description of the invention and the accompanying drawings is to be regarded as a non-limiting example thereof and that the scope of the invention of the protection is defined in the appended patent claims.