Patent Description:
Simulation system for simulating driving a car is used for both gaming as well as for training persons involved in driving vehicles such as racing car drivers.

A driving simulator can be defined as a system that simulates the operating conditions of a vehicle in an environment. Where the vehicle simulated is an automobile, the vehicle will usually include the typical automobile controls such as a steering wheel, a gear shift, an accelerator pedal, and a brake pedal. Generally, this vehicle will be simulated in an environment which will typically include a road.

Driving simulators provide a means to efficiently train operators of a vehicle. The operator of a vehicle can safely learn, from the simulator, how the vehicle will operate in a given set of conditions without actually exposing the operator to any of the risks inherent in real world operation of the vehicle. The experience garnered through making mistakes on a simulator is invaluable when compared to the inherent risks of vehicle damage and operator injury associated with making a driving error in a real-life situation. For example, in a police training application, a student could learn the limits of a police car or guidelines for pursuit and be tested in these areas without any of the associated risks of real-life training.

In addition to concerns relating to operator safety and vehicle damage, training through actual vehicle operation has other pitfalls. In particular, the cost of instructor time may be prohibitive. Furthermore, a specific vehicle such as a racing car or truck, may simply not be available for training purposes.

To enhance the effectiveness of the training afforded by driving simulators, there is a need to ensure that the simulator realistically simulates both the feel of operating the vehicle, as well as realistically simulating the effect of operating the various vehicle controls in specific situations. Realistically simulating the feel of operating a vehicle includes simulating the feel of the vehicle as it travels in a simulated environment as well as simulating the feel of the various vehicle controls during actual usage.

In driving simulators, the effectiveness of the training given by the simulator would be further enhanced if the feel of the brake pedal to the operator closely approximated the feel of an actual brake pedal in an actual car when the brake pedal is depressed. Further, the effect of depressing the brake pedal a given amount in the automobile simulator, as perceived by the operator (or user), should also closely approximate the effect that depressing the brake pedal the same amount has in a real-life automobile.

Today's automobiles are equipped with Anti-Lock Brake (ABS) systems. An ABS system is a safety feature added to automobiles to enhance the controllability of automobiles during braking manoeuvres. When non-ABS brakes are suddenly applied, or applied with great force, the brakes may lock up and consequently the automobile will often enter into an uncontrollable skid. An automobile tire will skid over the ground when the forward momentum of the automobile exceeds the velocity of the tire, thereby dragging the tire forward over the ground in a skidding fashion with less grip than when the wheel is rotating. An ABS brake system acts to prevent such uncontrollable skids by sensing when the tire is being dragged over the ground, and then decreasing the amount of stopping pressure exerted by the brakes against the wheel by an amount just sufficient to permit the tire to continue to roll over the ground while still slowing the rotation of the tire. The ABS system will then typically oscillate between increasing and decreasing the amount of braking force exerted against the brakes, and the braking force produced by the tire as the ABS system tries to slow the rotational velocity of the tires, while also preventing the brakes from locking up. This oscillation results in a unique, vibratory pulsation of the brake pedal during braking.

<CIT> discloses a vehicle simulator with realistic operating feedback. However, the vibratory pulsation of the brake pedal appearing when the ABS system is activated is generated by a single solenoid, which via an arm induces vibrations in the brake pedal. Although the simple mechanical system causes the brake pedal to vibrate, the feeling is not exactly the same as in real-life driving.

According to a first aspect of the present invention, a brake system for a driving simulator as described in claim <NUM> is provided.

The pressure system is adapted to intermittently increase and decrease the pressure in said hydraulic system such that tactile feedback is provided to said brake pedal.

By intermittently increasing and decreasing the pressure in the hydraulic system the resistance felt by a user applying force to the brake pedal will also intermittently change. When the pressure in the hydraulic system is decreased the brake pedal may be depressed under force applied by a user. When the pressure in the hydraulic system is increased it may work against the master piston and force the brake pedal towards the user in spite of the user applying pressure to the brake pedal. Alternating between these two situations will lead to vibrating tactile feedback for the user as the brake pedal moves intermittently in opposite directions.

Such tactile feedback provides the user with a tactical response during the driving simulation which closely corresponds to the tactile feeling of a brake pedal in a vehicle when ABS functionality is activated. Such life-like tactile response is beneficial as it enables more realistic simulation.

According to a further embodiment of the invention, the brake system comprises a pressure sensor for detecting the pressure within the hydraulic system and communicating the measurement to the driving simulator. The pressure sensor is arranged in fluid communication with the hydraulic system.

By having a pressure sensor arranged in fluid communication with the hydraulic system, the pressure within the hydraulic system may be detected. As the pressure correlates to the movement of the brake pedal through the movement of the master cylinder piston, the measurement of the pressure sensor corresponds to the force applied to the brake pedal. Hence the pressure sensor may provide the simulation software with a signal that can be used to determine the amount of braking of the simulated vehicle.

This pressure measurement may also be used to determine when an ABS braking session should be initiated. For example, an ABS braking session may be initiated when the magnitude of the detected pressure exceeds a predetermined thresholds for a predetermined duration.

According to a further embodiment of the invention, the first valve is a solenoid valve. A solenoid valve is particularly suited as it may be activated electronically by remote control thereby making it easily adapted for activation by a computer system controlling the simulation software.

According to the invention, the pressure module comprises a second valve which is adapted for temporarily closing and opening the fluid communication between the master side and the slave side of the hydraulic system. A benefit of enabling the pressure module to temporarily cut the connection between the master side of the hydraulic system and the slave side of the hydraulic system it becomes possible to control the pressure of the master side which is affecting the brake pedal and thus the tactile response without affecting the slave cylinder. According to a further embodiment of the invention, the second valve is a solenoid valve.

The pressure module comprises means for establishing a fluid connection between the pressure module and the hydraulic system.

By means of establishing a fluid connection is understood that the pressure module may be directly integrated in fluid conduits of the brake system or that it may comprise a fluid inlet and a fluid outlet for connecting to fluid conduits at a first end which at the second end are connected to a braking cylinder thereby forming the hydraulic system.

The hydraulic system comprises a master side and a slave side.

The pressure module further comprises an accumulator for increasing the volume and thereby decreasing the pressure of the hydraulic system.

The pressure module further comprises a pump for increasing the pressure of the hydraulic system.

The pressure module further comprises a first valve arranged to control the fluid communication between the accumulator and the master side of the hydraulic system.

The pressure module further comprises a second valve arranged to control the fluid communication between the master side and the slave side <NUM> of the hydraulic system.

The pump of the pressure module, the first valve and the second valve are configured to be controlled by a driving simulation software to provide a tactile feedback.

The driving simulator software may send signals to the components of the pressure module to activate the valves and/or pump in a sequence to provide tactile feedback through the brake pedal corresponding to the tactile response in a brake pedal of a vehicle during ABS braking. The simulation software may thus send signals to activate, i.e. to open and close, the first valve as well as the second valve. Similarly, the simulation software may send signals to turn on and off the pump of the pressure module.

According to a further embodiment of the first aspect of the invention, the first valve is a solenoid valve.

According to a further embodiment of the first aspect of the invention, the second valve is a solenoid valve.

According to a further embodiment of the first aspect of the invention, the pump is driven by a DC motor.

According to a second aspect of the present invention, a method of creating tactile feedback in braking system for a driving simulator as described in claim <NUM> is provided.

The method comprises the steps of providing a braking system with a pressure module. In response to a signal from a simulation software of said driving simulator an ABS braking session is begun. During said ABS braking session the pressure module alternates between two or more modes such that the pressure within a hydraulic system of the braking system varies during the ABS braking session regardless of the pressure applied to the brake pedal.

According to a further embodiment of the second aspect of the invention, one of the two modes is a pump mode during which a pump is activated to increase the pressure within the hydraulic system.

According to a further embodiment of the second aspect of the invention, one of the two modes is an accumulator mode wherein a first valve is activated to open and provide fluid communication between an accumulator and the hydraulic system, such that the volume is increased and the pressure is decreased.

According to a further embodiment of the second aspect of the invention, alternation between the two or more modes happens with a frequency in the range of <NUM>-<NUM>, more preferably with a frequency in the range of <NUM>-<NUM>.

These frequency ranges of the alternation between the two or more modes lead to the tactile response of the brake system happening at frequencies corresponding to those of an ABS braking system of a vehicle providing a life-like response. That is the movement of the brake pedal in response to the action of the pressure module will take place with a frequency such that the movement of the pedal in response to the simulation will take place at a frequency corresponding to the movement of a brake pedal of a vehicle in response to ABS braking.

The invention will now be described in further details with reference to drawings in which:.

The figures are only intended to illustrate the principles of the invention and may not be accurate in every detail. Moreover, parts which do not form part of the invention may be omitted. The same reference numbers are used for the same parts.

<FIG> illustrates a brake system for use with a driving simulator. The brake system comprises a brake pedal <NUM> that is connected to a brake cylinder <NUM>. The brake cylinder <NUM> may be a compact configuration as shown in <FIG> or the chambers of the brake cylinder may be split into different separated chambers. As schematically shown in <FIG> the brake cylinder <NUM> may be connected to a pressure module <NUM>. By connected is understood that they share at least a fluid connection. The pressure module may be connected to the brake cylinder <NUM> and located away from the brake cylinder <NUM> itself. In other embodiments based on the same working principle the pressure module <NUM> may be integrated with or mounted directly to the brake cylinder <NUM>.

In a preferred embodiment the brake pedal <NUM> and brake cylinder <NUM> are mounted to a support surface <NUM>. The brake pedal <NUM> may in a preferred embodiment be mounted via a pivot axis <NUM> on a support surface <NUM> which is adapted to ensure that the brake system is supported in a stable manner as the area of the support surface <NUM> is larger than the area of the mounted pedal <NUM> and brake cylinder <NUM> projected onto the plane of the support surface such that it increases the area of contact between the brake system and the surface on which the brake system is located thus decreasing the risk of the brake system tilting during use. The support surface <NUM> further contributes weight such that the centre of mass of the brake system is lowered, thereby further increasing the stability of the position of the brake system, when it is in use.

The brake system is adapted to communicate with a computer running car simulation software, the communication between the brake system and a computer system could be via wires such as USB or wireless such as Bluetooth. The communication should preferably be real-time (or at least close to real time due to computational limits of processing inputs and data in a modern computer) to ensure that any actions on the brake pedal is immediately communicated to the software for instant reactions and a realistic feel in the simulation software. The communication may include exchange of information, for example a sensor of the brake system may supply the computer system with sensor data relating to the amount of force applied to the brake pedal <NUM>. The simulation software of the computer system may also control part of the brake system, e.g. controlling when an ABS braking session is activated, i.e. when it begins and when it ends, as it may at least in part control the activation of the active components of the brake system.

During operation when the brake pedal <NUM> is depressed, that is when a user begins to apply force to the brake pedal, force is transferred to a master cylinder rod <NUM> which causes the movement of pistons within the brake cylinder <NUM> and in turn changes the pressure within the brake cylinder <NUM>. A sensor <NUM> detects the pressure within the brake cylinder <NUM> and communicates this back to the computer system. The sensor is able to both detect when, how much, and how fast pressure on the brake pedal is changed. The simulation software then correlates this pressure measurement with a braking force.

The brake cylinder is connected to the brake pedal <NUM> by a rod connector <NUM>, at the end of the piston rod of the master cylinder piston <NUM>. The rod connector <NUM> connects to a mount plate <NUM> on an arm of the brake pedal <NUM>. In a preferred embodiment the rod connector <NUM> is a rod clevis which connects to the mount plate <NUM> by gripping around the mount plate <NUM> and being releasably fixed by fixing means such as a screw or bolt.

The movement of the brake pedal <NUM> when the user applies force to the brake pedal <NUM>, i.e. when it is depressed, is considered that the brake pedal <NUM> moves forwards. The opposite direction of movement of the brake pedal <NUM>, i.e. the direction that the pedal moves as the application of force to the brake pedal <NUM> is decreased, is considered that the brake pedal <NUM> moves backwards.

<FIG> schematically illustrates the components of the brake system, the components are not to scale.

The brake cylinder <NUM> comprises a master cylinder chamber <NUM> and a slave cylinder chamber <NUM>. In some preferred embodiments the master cylinder chamber <NUM> and the slave cylinder chamber <NUM> may be integrated in the same housing of the brake cylinder as shown in <FIG>. In alternative preferred embodiments the master cylinder chamber <NUM> and the slave cylinder chamber <NUM> may be two separate units.

The master cylinder piston <NUM> is adapted to translate inside the master cylinder chamber <NUM> along the axis of the master cylinder chamber <NUM> when the brake pedal <NUM> is being pressed. The movement of the master cylinder piston <NUM> acts upon a hydraulic fluid in the master cylinder chamber <NUM>.

The slave cylinder chamber <NUM> of the brake cylinder <NUM> comprises a slave cylinder piston <NUM>. The slave cylinder piston <NUM> is connected with a damper system <NUM> via a slave cylinder rod <NUM>. The damper system <NUM> is configured to control the stiffness and length of the brake pedal <NUM>. In some preferred embodiments the damper system <NUM> is configured to enable user adjustment of the stiffness and length of the brake pedal <NUM>. The slave cylinder piston <NUM> is adapted to translate along the axis of the slave cylinder chamber <NUM>. Such translation happens in response to hydraulic forces in the brake cylinder <NUM>.

The master cylinder chamber <NUM> and the slave cylinder chamber <NUM> are in fluid communication such that the exchange of hydraulic fluid between the chambers <NUM>,<NUM> is possible. The hydraulic communication of the chambers is facilitated by fluid conduits. A pressure module <NUM> is connected to those fluid conduits such that the hydraulic communication between the master cylinder chamber <NUM> and the slave cylinder chamber <NUM> takes place via the pressure module <NUM>.

In other words the hydraulic system <NUM> of the invention includes and extends from the master cylinder chamber <NUM> to the slave cylinder chamber <NUM> via the pressure module <NUM>. The hydraulic system <NUM> thus forms a fluid connection between the master cylinder chamber <NUM> and the slave cylinder chamber <NUM>.

The pressure module <NUM> divides the hydraulic system <NUM> into a master side <NUM> and a slave side <NUM>, such that the master side <NUM> is the side including the master cylinder chamber <NUM>, and the slave side is the side including the slave cylinder chamber <NUM>.

The pressure module <NUM> includes a first valve <NUM> and a second valve <NUM>. In a preferred embodiment of the invention the first valve <NUM> and/or the second valve <NUM> are solenoid valves.

The second valve <NUM> is arranged such that it can open and close the fluid connection between the master side <NUM> and the slave side <NUM> of the hydraulic system <NUM>. When the second valve <NUM> is open the master side <NUM> and the slave side <NUM> are in fluid communication. When the second valve <NUM> is closed the fluid connection between the master side <NUM> and the slave side <NUM> is cut off. Thus the pressure module <NUM> controls the connection between the master side <NUM> and the slave side <NUM> in the hydraulic system <NUM>.

The pressure module <NUM> further comprises an accumulator <NUM>. The accumulator <NUM> forms a chamber with a volume. The first valve <NUM> is arranged to open and close the connection of the accumulator to the master side <NUM> of the hydraulic system <NUM>. When the first valve <NUM> is open the accumulator is in fluid communication with the master side <NUM> of the hydraulic system <NUM> thereby increasing the active volume of the hydraulic system <NUM>. When the first valve <NUM> is closed, the accumulator <NUM> is cut off from the remained of the hydraulic system <NUM>, thereby limiting the volume of the hydraulic system <NUM>.

In a preferred embodiment of the invention the valves <NUM> and <NUM> are controlled by the simulation software. In such embodiments the simulation software can then activate the ABS braking mode in response to the simulation situation where ABS would be appropriate for example due to road conditions or in response to a braking signal exceeding a threshold value in magnitude and/or duration.

The pressure module further comprises a pump <NUM>. In a preferred embodiment the pump <NUM> is driven by a DC motor <NUM>. The pump is arranged such that it may increase the pressure in the hydraulic system <NUM>, when it is activated.

Hence, the translation of the master cylinder piston <NUM> within the master cylinder chamber <NUM> may be due to any of the following: The depression of the brake pedal <NUM>, release of the brake pedal <NUM> and backaction of the system action upon the master cylinder piston <NUM>, or increased pressure in the hydraulic system <NUM> caused by the activation of the pump <NUM> of the pressure module <NUM> which will force the brake pedal <NUM> back towards its default, non-depressed position.

While the pressure module <NUM> is in the schematic <FIG> depicted as a region of the combined brake system including a number of features, it is to be understood that in practice the pressure module <NUM> may be one or more separate components with fluid inlets and fluid outlets for releasably connecting the pressure module <NUM> to the brake cylinder <NUM> via fluid conduits. Such assembly of the brake system has the benefit of easier maintenance and the exchange of worn components.

While not depicted in <FIG> the brake system further comprises a pressure sensor. The pressure sensor may be mounted anywhere in fluid communication with the hydraulic system <NUM>. For example it may be connected to either of the cylinder chambers <NUM>, <NUM> as shown in <FIG> or as another example it may be connected to the hydraulic system as part of the pressure module <NUM>. In yet other exemplary variants the sensor may be connected separately to a fluid conduit of the brake system.

The <FIG> schematically illustrate the pressure module in different modes of operation. In the <FIG> a valve is schematically depicted as closed if it is diagonally hatched, while it is depicted as open if it has no hatching. A fluid conduit is depicted as being in fluid communication with the master cylinder chamber if it has circle hatching; note that the hatching is simply schematic illustration and does not indicate the actual distribution of a fluid flow through the valves, only that the valve is open or closed.

<FIG> schematically illustrates a first mode of the pressure module <NUM>, where the brake system is in the normal braking mode, i.e. the default situation without the application of ABS. This normal braking mode is employed during normal driving, i.e. as opposed to ABS braking conditions, and occurs when the braking force does not exceed threshold conditions of amplitude and/or duration. In this normal driving and normal braking mode, the simulation software will not activate the ABS simulator system in the brake system.

In this default state for normal braking conditions the first valve <NUM> is closed, such that the accumulator <NUM> is cut off from the rest of the hydraulic system and the second valve <NUM> is open such that there is fluid communication between the master cylinder chamber and the slave cylinder chamber.

In this default state for normal braking, when the brake pedal <NUM> is depressed as force is applied to the brake pedal <NUM> this force will be translated from the pedal to the master cylinder piston <NUM> which in turn will cause the master cylinder piston <NUM> to act upon the hydraulic fluid within the master cylinder chamber <NUM>. The force applied to the hydraulic fluid in the master cylinder chamber <NUM> will force the hydraulic fluid from the master cylinder chamber <NUM> through the fluid conduits of the hydraulic system <NUM>. As the second valve <NUM> is open the hydraulic fluid will be forced to the slave cylinder chamber <NUM> where the pressure of the fluid activates the slave cylinder piston <NUM>. The slave cylinder piston <NUM> interacts with the damper system <NUM>, e.g. by compressing a damper in the damper system <NUM> and/or by contacting a mechanical block. As force is applied to the brake pedal <NUM> and resistance is provided by the damper system <NUM> the hydraulic fluid is pressed between the master cylinder piston <NUM> and the slave cylinder piston <NUM> causing the pressure within the hydraulic system <NUM> to rise. The increase in pressure is detected by a pressure sensor in fluid communication with the hydraulic system <NUM>.

During normal braking operation, i.e. when the simulation software does not indicate a need for emulation of ABS braking conditions, the pressure module <NUM> remains in the default state illustrated in <FIG>, i.e. with the first valve <NUM> closed and the second valve <NUM> open. The user will feel the brake pedal <NUM> depress as force is applied, possibly followed by a period of little to no movement being felt by the user as the pressure increases in the hydraulic fluid.

When the user releases the brake pedal <NUM>, i.e. by applying diminishing or no force to the brake pedal <NUM>, the brake pedal <NUM> will return to its default position. The pressure in the hydraulic system <NUM> will decrease once again and both the slave cylinder position <NUM> and the master cylinder piston <NUM> will move back to their default positions. In preferred embodiments the brake cylinder comprises resilient structures such as resilient materials and/or springs which are arranged to apply force to the slave cylinder piston <NUM> and/or the master cylinder piston <NUM> in such a way that they are urged back to their default position when no pressure is applied to the brake pedal <NUM>.

The simulator software controls the activation of the ABS simulator system for example due to conditions of the simulated world such as braking when the simulated vehicle is on a specific type of simulated surface or in response to the sensor data from the pressure sensor exceeding a threshold condition, or it could be activated by the software e.g. due to a detection of the left front wheel not moving or moving slower than the other wheels or just based on a reading from the pressure sensor detecting that the brake pressure is above a specific threshold value. When the ABS simulator system is activated, the brake system will alternate between different modes of the system. As the different modes change the pressure in the hydraulic system <NUM>, they will affect the resistance felt during application of pressure to the brake pedal <NUM> causing a tactile response for the user stepping on the brake pedal <NUM>. Preferably the change of operation modes of the pressure module <NUM> during the ABS braking session happens rapidly in short intervals giving the feeling of vibration or jerking of the pedal corresponding to the feeling when an ABS system is activated in real-life driving. For example the change of modes in the pressure module <NUM> during an ABS braking session may take place with a frequency which can be adjusted by the user to achieve the best and most realistic feeling for a given vehicle. In a preferred embodiment the frequency of mode change during an ABS braking session is <NUM>-<NUM>, more preferably <NUM>-<NUM>. By an ABS braking session is understood the period from the beginning of ABS braking mode until the end of ABS braking mode and return to the normal braking mode, described in relation to the default configuration illustrated in <FIG>.

<FIG> illustrates a second mode of the pressure module <NUM> also called the closed mode. In the closed mode the first valve <NUM> will remain closed and the second valve <NUM> will also close. As the second valve <NUM> closes, the master side <NUM> and the slave side <NUM> of the hydraulic system <NUM> are cut off from each other. It is noted that the hydraulic fluid is not evacuated from the slave side <NUM> of the hydraulic system <NUM> but that hatching is an indication of fluid communication with the master side <NUM> simply for illustrative purposes of the effect of the valves.

As the second valve <NUM> closes and the slave side <NUM> is cut off from the master side <NUM>, applying pressure to the brake pedal <NUM> will still cause the pressure in the master side <NUM> of the brake system to increase but the slave cylinder piston <NUM> will not move any further. The resistance experienced by the user applying force to the brake pedal <NUM> is thus that of compressing the brake fluid. For liquids which are low- or non-compressible fluids the resistance experienced will be high and the brake pedal <NUM> will feel immovable to the user. In embodiments of the invention the pressure sensor is connected to the slave side <NUM> of the hydraulic system <NUM>, the detected pressure will remain constant when the second valve <NUM> is activated, regardless of the force applied to the brake pedal <NUM>. In embodiments of the brake system, wherein the pressure sensor is connected to the master side <NUM> of the hydraulic system <NUM> any increase in the pressure due to force exerted on the brake pedal <NUM> will be registered in this mode of the ABS braking session.

<FIG> illustrates a third mode of the pressure module <NUM> also called the accumulator mode. In the accumulator mode, the first valve <NUM> is open whereby the accumulator <NUM> is in fluid communication with the master side <NUM> thereby increasing the volume of the master side <NUM>. The second valve <NUM> is closed such that the master side <NUM> is cut off from the slave side <NUM> of the hydraulic system <NUM>. In the accumulator mode as the first valve <NUM> opens and the volume of the master side <NUM> increases, the pressure in the master side decreases. The decrease in pressure will lower the resistance that the user feels when pressing on the pedal. With the increased volume the pedal will be able to move a further distance under the same applied force, than it could before the volume increase, i.e. when the first valve <NUM> is closed. This is called that the pedal is made longer, as the pedal can move a further distance under the same pressure. As the volume change happens immediately when the first valve <NUM> opens, the change of the resistance of the brake pedal <NUM> will be a sudden change, causing the user's foot to jerk forward, as the ABS braking session will begin at a point where the user is applying force to the brake pedal <NUM>.

<FIG> schematically illustrates a fourth mode of the pressure module <NUM>, also called the open mode, wherein both the first valve <NUM> and second valve <NUM> are open. In this situation the accumulator <NUM> is in fluid communication with the remainder of the hydraulic system <NUM> contributing to an increased volume.

Simultaneously the master side <NUM> and the slave side <NUM> of the hydraulic system <NUM> is in communication. This mode may be an alternative default mode to the mode shown in <FIG>, as the master cylinder chamber and the slave cylinder chamber are in fluid communication the normal mode braking operation is achieved in this mode.

The increase of the volume in fluid communication with the master side <NUM> of the hydraulic system <NUM> by opening the first valve <NUM> and granting fluid access to the accumulator <NUM>, has the same effect on lowering the resistance felt by the user applying pressure to the brake pedal <NUM>, regardless of whether the second valve <NUM> is open or closed. Hence, if the state of the first valve <NUM> changes from closed to open the user will feel the brake pedal <NUM> getting longer and jerk forward under the pressure applied by the user in either of the configurations of <FIG>.

While not illustrated in the figures a fifth mode of the pressure module <NUM> exists and is also called the pump mode. In the pump mode the pump <NUM> is activated. The pump <NUM> is configured to increase the pressure in the hydraulic system <NUM>. As the pressure in the hydraulic system <NUM> is increased it will increase the force applied to the master cylinder piston <NUM> in the opposite direction of the force applied by the user depressing the brake pedal <NUM>. This will cause the resistance also called the counter-force on the brake pedal <NUM> to increase. Hence, the pressure increase caused by the activation of the pump <NUM> causes the brake pedal <NUM> to move backwards towards the user applying force to the brake pedal <NUM>, giving a tactile feedback of push against the user's foot.

It is to be understood that the pump mode may be engaged simultaneously with any of the other modes described for the pressure module <NUM>. That is the pump <NUM> may be activated regardless of the state of the first valve <NUM> and the second valve <NUM>, i.e. regardless of whether they are opened or closed.

Different ABS experiences may be achieved by alternating or cycling the various described modes in rapid succession throughout an ABS braking session.

In one example of a preferred embodiment, once the simulation software signals the beginning of an ABS braking session the second valve <NUM> will close whereby the master side <NUM> and the slave side <NUM> of the hydraulic system <NUM> are separated. While the second valve <NUM> remains closed the pressure module <NUM> will alternate between opening the first valve <NUM> and activating the pump <NUM>. When the first valve <NUM> is opened the volume of the master side <NUM> of the hydraulic system <NUM> is increased such that the pressure is decreased and the brake pedal <NUM> will jerk forward if the user maintains the same pressure applied to the brake pedal <NUM> as before the opening of the first valve <NUM>. When the pump <NUM> is then activated the pressure in the master side <NUM> of the hydraulic system <NUM> will increase forcing the master cylinder piston <NUM> and the brake pedal <NUM> backwards, creating a push against the foot of the user applying pressure to the brake pedal <NUM>. As the pressure module <NUM> alternates between these modes with a respectively lower and higher pressure throughout the ABS braking session, the brake pedal <NUM> will move rapidly forwards and backwards while the user applies pressure to the brake pedal <NUM>, giving the user tactile feedback corresponding to the feedback felt when the ABS of a real vehicle is engaged. In a preferred embodiment the alternation between the modes in the ABS braking session happens with a frequency between <NUM>-<NUM>, more preferably between <NUM>-<NUM>. Such frequency makes the movement of the brake pedal <NUM> give the user a tactile feedback in the form of vibration.

Once the simulation software sends signal that the ABS braking session has ended the pressure module <NUM> will revert back to the normal state, wherein the master side <NUM> and the slave side <NUM> of the brake system are in fluid communication.

In other equally preferred embodiments the mode alteration during an ABS braking session may be different from the previously described example. For example in some embodiments the first valve <NUM> may remain open throughout the ABS braking session while the pump <NUM> is turned on and off to cause the vibrating response. In other variants the pump <NUM> may be configured to activate when the first valve <NUM> is closed and to turn off when the first valve <NUM> is opened. In some embodiments the second valve <NUM> may close at the beginning of the ABS braking session and open at the end of the ABS braking session. In other embodiments the opening and closing of the second valve <NUM> may also alternate throughout the braking session.

When the braking session with the ABS simulator system is finished the second valve <NUM> is opened such that the connection between the master side <NUM> and the slave side <NUM> is opened and the valve <NUM> closed such that the volume of hydraulic liquid is adjusted to the volume present in the hydraulic system before the braking session.

Claim 1:
A driving simulator brake system characterized in that it comprises a hydraulic system, said hydraulic system comprising a pressure module, said pressure module being in fluid communication with said hydraulic system <NUM>, said hydraulic system <NUM> comprising a master side <NUM> and a slave side <NUM>, said pressure module <NUM> comprising:
an accumulator <NUM> for increasing the volume and thereby decreasing the pressure of the hydraulic system <NUM>;
a pump <NUM> for increasing the pressure of the hydraulic system <NUM>,
a first valve <NUM> arranged to control the fluid communication between said accumulator <NUM> and said master side <NUM>;
a second valve <NUM> arranged to control the fluid communication between said master side <NUM> and said slave side <NUM> of said hydraulic system <NUM>,
wherein said pump <NUM>, said first valve <NUM> and said second valve <NUM> are configured to be controlled by a driving simulation software to provide a tactile feedback to the master side by alternately opening and closing the first valve or the second valve.