Patent Description:
<CIT> and <CIT> disclose an enhanced steering control system for a steering system of a recreational vehicle including one or more mechanical dampers coupled to the steering system that resist movement of the steering system, the enhanced steering control system comprising: an electrically actuated device adapted to be coupled to the steering system for applying force to the steering system; a sensor adapted to be positioned adjacent the steering system when the electrically actuated device is coupled to the steering system that generates data indicating an operational state of the recreational vehicle; and a controller coupled to the electrically actuated device and the sensor and configured to: estimate a first torque applied to the steering system by the one or more mechanical dampers based on the operational state; calculate a second torque to apply to the steering system by the electrically actuated device based on the estimated first torque and the operational state; and operate the electrically actuated device to apply the second torque to the steering. <CIT> further discloses that the controller is configured to estimate the first torque applied to the steering system by the one or more mechanical dampers based on the operational state by being configured to: apply the operational state to a model specific to each of the one or more mechanical dampers to determine a third torque applied to the steering system by the mechanical damper, and estimate the first torque applied to the steering system by the one or more mechanical dampers based on the third torque estimated for each of the one or more mechanical dampers.

According to the present invention an enhanced steering control system for a steering system of a recreational vehicle is provided which steering control system comprises the features of claim <NUM>.

The unique steering dynamics and intense environmental conditions of recreational vehicles can provide a driving feel that is quite different from that of the typical automobile. For instance, typical personal watercraft (PWC) type recreational vehicles have steering dynamics that provide little or no feedback to the driver and deliver tremendous cornering forces at high speeds via very light steering effort. Specifically, the steering system of the typical PWC provides little or no feedback to the driver of the forces exchanged between the PWC and its environment, such as during a turn. The steering handle of the typical PWC also has less than a ninety-degree lock-to-lock range, which offers very quick but low-resolution steering control. Conversely, the drivetrain of a typical automobile provides relatively high steering feedback to the driver, and includes a steering wheel having a multi-turn (e.g., three turns) lock-to-lock range, which offers high resolution steering control at the expense of increased driver effort to generate high steering rates.

An unexperienced driver of the typical PWC, who may be used to the driving feel of an automobile, may associate the lack of steering feedback and ease of steering provided by the PWC with a lack of responsiveness or control. This association may lead the driver to perform dangerous maneuvers, such as excessive steering operations at high speeds that eject the driver from the PWC. To provide increased steering feedback and discourage dangerous maneuvers, recreational vehicles like the PWC may be equipped with an enhanced steering control system described herein.

<FIG> illustrates a personal watercraft (PWC) <NUM> with an enhanced steering control system <NUM> that may be configured to provide increased steering feedback to a driver. As described in more detail below, the enhanced steering control system may utilize a combination of one or more mechanical dampers <NUM> and an electrically actuated device (EAD) <NUM> to apply torque to the steering system of the PWC <NUM> as a function of the operational state the PWC <NUM>, and thereby provide increased steering feedback to the driver. The EAD <NUM> is implemented to apply the increased steering feedback, utilizing the EAD <NUM> in combination with mechanical dampers <NUM> which reduces the needed size of the EAD <NUM>, and may reduce the electrical load required to provide the desired steering feedback.

The PWC <NUM> may include a jet powered propulsion system <NUM>, a steering system <NUM>, and the enhanced steering control system <NUM>. The jet powered propulsion system <NUM> may be configured to propel the PWC <NUM> in a forward direction. The steering system <NUM> may be coupled to the jet powered propulsion system <NUM>, and may be configured to adjust the angle of the jet powered propulsion system <NUM> relative to the hull of the PWC <NUM> to steer the PWC <NUM> in a given direction. The enhanced steering control system <NUM> may be coupled to the steering system <NUM>, and may be configured to implement enhanced steering control for the PWC <NUM>.

The jet powered propulsion system <NUM> may include an engine <NUM>, a turbine <NUM>, a nozzle <NUM>, and a throttle <NUM>. The throttle <NUM> may be connected to a steering handle <NUM> of the PWC <NUM>, and may be coupled to the turbine <NUM>, such as via the engine <NUM>. A driver may actuate with the throttle <NUM> to cause the engine <NUM> to rotate the turbine <NUM>. Acceleration of the PWC <NUM> may correspond to the rotational speed of the turbine <NUM>, which may correspond to the extent of actuation of the throttle <NUM> by the driver. For instance, the throttle <NUM> may form a rotatable grip secured to an end the steering handle <NUM>. The greater the rotation of the throttle <NUM>, the faster the engine <NUM> may rotate the turbine <NUM>, and the faster the turbine <NUM> may propel the PWC <NUM> in the forward direction.

Rotation of the turbine <NUM> may drive water into an input end of the nozzle <NUM>. The nozzle <NUM> may responsively form a hydraulic jet stream that is expressed away from the PWC <NUM> through an output end of the nozzle <NUM>. The jet stream may function to propel the PWC <NUM> in the forward direction. When the nozzle <NUM> expresses a jet stream in a direction parallel and/or collinear to a longitudinal axis of the PWC <NUM> (i.e., the axis extending through the center of the stern and bow of the PWC <NUM>), the jet stream may propel the PWC <NUM> in a straight forward direction.

The steering system <NUM> may include the steering handle <NUM>, a steering column <NUM>, a gearbox <NUM>, and a push-pull cable <NUM>. Rotation of the steering handle <NUM> left and right may cause the PWC <NUM> to turn left and right respectively. Specifically, the steering handle <NUM> may be coupled to the gearbox <NUM> via the steering column <NUM>. Rotation of the steering handle <NUM> by a driver may cause a corresponding rotation of the steering column <NUM>, which may be received by the gearbox <NUM>. The gearbox <NUM> may be coupled to the nozzle <NUM> via the push-pull cable <NUM>, and may be configured to translate a rotation of the steering column <NUM>, such as via one or more gears, into a push or pull force onto an end of the push-pull cable <NUM> connected to the gearbox <NUM>. Responsive to the push or pull force being applied to the connected end of the push-pull cable <NUM>, the other end of the push-pull cable <NUM> may exert a respective push or pull force onto the nozzle <NUM>. The push or pull force applied to the nozzle <NUM> may cause the output end of the nozzle <NUM> to pivot with respect to the longitudinal axis of the PWC <NUM>. In alternative examples, rather than the gearbox <NUM>, the PWC <NUM> may include a different mechanism, such as an armlink or an electronic actuator, between the steering handle <NUM> and the nozzle <NUM> that is configured to translate a rotation of the steering handle <NUM> into a pivoting steering force applied to the nozzle <NUM>.

Setting the nozzle <NUM> at a non-parallel angle to the longitudinal axis of the PWC <NUM>, which may correspondingly set the jet stream at a non-parallel angle to the longitudinal axis, may cause the PWC <NUM> to turn in a direction corresponding to the direction of the jet stream. Specifically, as the output end of the nozzle <NUM> pivots away from the longitudinal axis of the PWC <NUM> responsive to a rotation of the steering handle <NUM> to perform a turn, the jet stream formed by the nozzle <NUM> may cause the hull of the PWC <NUM> to lean towards the turn. The hull's geometry, which may include ridges or other fixed control surfaces, may correspondingly interact with the water on the inside the turn. This interaction may effect turning the PWC <NUM> under the power of the jet stream.

For instance, a clockwise rotation of the steering handle <NUM> may cause a corresponding clockwise rotation of the steering column <NUM>. The gearbox <NUM> may be configured to translate the clockwise rotation of the steering column <NUM> into a pull force on the push-pull cable <NUM>, which may responsively exert a pull force on the nozzle <NUM>. This pull force may cause the output end of the nozzle <NUM> to pivot right (or counter-clockwise), thereby causing the jet stream to push the back end of the PWC <NUM> left and effect a right turn of the PWC <NUM>. Similarly, a counter-clockwise rotation of the steering handle <NUM> may cause a corresponding counter-clockwise rotation of the steering column <NUM>. The gearbox <NUM> may be configured to translate this counter-clockwise rotation of the steering column <NUM> into a push force on the push-pull cable <NUM>, which may responsively exert a push force on the nozzle <NUM>. This push force may cause the output end of the nozzle <NUM> to pivot left (clockwise), thereby causing the jet stream to push the back end of the PWC <NUM> right and effect a left turn of the PWC <NUM>.

The enhanced steering control system <NUM> may be coupled to the steering system <NUM> of the PWC <NUM>, and may be configured to increase steering feedback felt by the driver during operation of the PWC <NUM>. The steering control system <NUM> may include an electronic control system <NUM> and one or more mechanical dampers (MDs) <NUM>. The electronic control system <NUM> may include an electrically actuated device (EAD) <NUM>, an electronic control unit (ECU) <NUM>, and one or more sensors <NUM>.

The EAD <NUM> may be coupled to the steering system <NUM> and the ECU <NUM>, and may operate as an electric power steering (EPS) unit for the PWC <NUM>. Specifically, the EAD <NUM> may be configured, such as at the direction of the ECU <NUM>, to apply force to the steering system <NUM>. The applied force may increase steering feedback felt by the driver during operation of the PWC <NUM>.

The EAD <NUM> may include a motor <NUM>, such as an electric motor, for applying the force to the steering system <NUM>. The motor <NUM> may be coupled to the steering column <NUM>, such as through the gearbox <NUM> and via a motor shaft <NUM> rotatable by the motor <NUM>. During operation of the PWC <NUM>, the gearbox <NUM> may receive rotations of the motor shaft <NUM> by the motor <NUM>, and may be configured to translate these rotations into corresponding forces applied to the steering system <NUM>. For instance, the gearbox <NUM> may be configured to translate the rotation of the motor shaft <NUM> into a torque applied to the steering handle <NUM> and the steering column <NUM>, and correspondingly into a push or pull force applied to the push-pull cable <NUM> and nozzle <NUM>. In one example, the applied forces may resist rotation of the steering handle <NUM> by the driver.

Rather than applying force to the steering system <NUM> through the gearbox <NUM>, the EAD <NUM> may be coupled to and apply the torque to the steering column <NUM> directly. For instance, the EAD <NUM> may include one or more arms coupled to the steering column <NUM> that are rotatable by the motor <NUM> to apply torque to the steering column <NUM>, may include a sleeve through which the steering column <NUM> extends and is coupled to that is rotatable by the motor <NUM> to apply torque to the steering column <NUM>, may include a belt that wraps around the steering column <NUM> and is rotatable by the motor <NUM> to apply torque to the steering column <NUM>, or may include a gear that interacts with a corresponding geared portion of the steering column <NUM> and is rotatable by the motor <NUM> to apply torque to the steering column <NUM>.

The ECU <NUM> (also referred to herein as a "controller") may be configured to communicate with other components of the PWC <NUM>, or more particularly with other components of the electronic control system <NUM>, directly and/or over one or more networks, such as a control area network (CAN), and through wired and/or wireless connections. During operation of the PWC <NUM>, the ECU <NUM> may be configured to operate the EAD <NUM> to apply force to the steering system <NUM> based on data received from the sensors <NUM>. Additional details of the configuration of the ECU <NUM> are provided below.

The one or more sensors <NUM> may be configured to generate data (also referred to herein as "sensor data") indicating the current operational state of the PWC <NUM>. At least one of the sensors <NUM> may be positioned adjacent the steering system <NUM>, and may be configured to generate sensor data indicating the current operational state of the steering system <NUM>.

For instance, the sensors <NUM> may include a steering angle sensor positioned adjacent the steering system <NUM> and configured to generate sensor data indicating a current angle of the steering system <NUM>, or more particularly of the steering handle <NUM> and/or nozzle <NUM>, such as relative to a center position of the steering system <NUM> (e.g., a position in which the nozzle <NUM> and jet stream are parallel with the longitudinal axis of the PWC <NUM>). A steering angle of zero may correspond to the steering system <NUM> being located at its center position, a positive steering angle may correspond to the steering system <NUM> being off-center in one direction (e.g., clockwise direction), and a negative angle may correspond to the steering system <NUM> being off-center in the other direction (e.g., counterclockwise direction). The magnitude of the steering angle may represent the difference between the current angle of the steering system <NUM> and its center position.

The sensor data generated by the steering angle sensor may also indicate the steering rate of the steering system <NUM>. Specifically, the ECU <NUM> may be configured to track the steering angle of the steering system <NUM> indicated by the steering angle sensor over time, and to determine the rate and direction that the steering system <NUM>, or more particularly the steering handle <NUM> and steering column <NUM>, is being rotated based thereon. The magnitude of the steering rate may correspond to the speed of rotation, and the sign of the steering rate may correspond to the direction of rotation. For instance, the ECU <NUM> may be configured to indicate a positive steering rate when the steering angle sensor data indicates rotation of the steering handle <NUM> in the clockwise direction, and indicate a negative steering rate when the steering rate sensor data indicates rotation of the steering handle <NUM> in the counterclockwise direction.

The sensors <NUM> may also include a torque sensor positioned adjacent the steering system <NUM> and configured to generate sensor data indicating a magnitude and direction of torque on the steering system <NUM>, or more particularly on the steering column <NUM> and the steering handle <NUM>. The sensors <NUM> may further include a rotation sensor configured to generate sensor data indicating the current rotational speed of the engine <NUM> and/or turbine <NUM>, a throttle request sensor configured to generate sensor data indicating an extent to which the driver is currently actuating the throttle <NUM>, which may be represented by a numerical value that increases with increased actuation of the throttle <NUM>, and a speed sensor configured to generate sensor data indicating the current speed of the PWC <NUM>. The sensors <NUM> may additionally include a navigation system, which may include a global positioning system (GPS) and/or an inertial measurement system (IMS), configured to generate sensor data indicating a current position of the of the PWC <NUM>.

The sensor data generated by the above sensors <NUM> may indicate the current velocity (e.g., speed and heading) and acceleration level of the PWC <NUM>. For instance, the ECU <NUM> may be configured to determine the current velocity and acceleration level of the PWC <NUM> based on speeds generated by the speed sensor over time, and/or based on positions of the PWC <NUM> generated by the navigation system over time. The ECU <NUM> may further be configured to determine the current acceleration level of the PWC <NUM> based on a current speed of the PWC <NUM> generated by the speed sensor, and a current rotational speed of the engine <NUM> and/or turbine <NUM> generated by the rotational sensor or a throttle request extent of indicated by the throttle request sensor. For instance, the ECU <NUM> may be configured to determine an acceleration level of the PWC <NUM> based on these operational parameter values by applying the values to a stored look-up table that associates varying possible operational states each setting forth possible values for these operational parameters with different acceleration levels.

The one or more mechanical dampers <NUM> may be coupled to the steering system <NUM>, such as to the steering column <NUM>, and may be configured to provide increased steering feedback during movement of the steering system <NUM>. Specifically, the one or more mechanical dampers <NUM> may be configured to resist movement of the steering system <NUM>, or more particularly rotation of the steering handle <NUM> and the steering column <NUM>, such as to necessitate increased effort to change the angle of the steering system <NUM> of the PWC <NUM>. At least one of the mechanical dampers <NUM> may be configured to resist movement of the steering system <NUM> from its center position, and at least one of the mechanical dampers <NUM> may be configured to resist movement of the steering system <NUM> towards the center position. At least one of the mechanical dampers <NUM> may also be configured to bias the steering system <NUM> towards the center position, such as to provide a self-centering function. The one or more mechanical dampers <NUM> may thus facilitate providing a driving feel that is closer to that of a typical automobile.

For example and without limitation, the one or more mechanical dampers <NUM> may include a spring type mechanical damper 128A, a fluid type mechanical damper 128B, and/or a friction type mechanical damper 128C. The spring type mechanical damper 128A may include a spring that compresses with movement of the steering system <NUM> from the center position, and decompresses with movement of the steering system <NUM> to the center position. The torque applied by the spring type mechanical damper 128A to the steering system <NUM> may be a function of the angle of the steering system <NUM>. Specifically, the spring type mechanical damper 128A may be configured to apply increased torque in the direction of the center position of the steering system <NUM> as the steering handle <NUM> rotates further from the center position, and to apply decreased torque in the direction of the center position of the steering system <NUM> as the steering handle <NUM> rotates towards the center position. The spring type mechanical damper 128A may also bias the steering system <NUM> to the center position, such as to provide a self-centering function when the driver is providing little or no torque to the steering handle <NUM>.

The fluid type mechanical damper 128B may include a plunger configured to push fluid between fluid chambers with movement of the steering system <NUM>, where the fluid resists movement of the plunger. The torque applied by the fluid type mechanical damper 128B to the steering system <NUM> may be a function of the steering rate of the steering system <NUM>. Specifically, the fluid type mechanical damper 128B may apply increased torque to the steering system <NUM> in a direction opposite the direction of rotation of the steering handle <NUM> as the steering rate of the steering system <NUM> increases. In some instances, the fluid type mechanical damper 128B may be a magnetorheological (MR) fluid damper in which a varying magnetic field is applied to MR fluid contained in the chambers that alters the viscosity of the fluid and correspondingly adjusts the dampening response provided by the damper.

The friction type mechanical damper 128C may include a friction disc configured to resist rotation with movement of the steering system <NUM>. The torque applied by the friction type mechanical damper 128C to the steering system <NUM> may be a function of the steering rate of the steering system <NUM>. Specifically, the friction type mechanical damper 128C may apply increased torque to the steering system <NUM> in a direction opposite the direction of rotation of the steering handle <NUM> as the steering rate of the steering system <NUM> increases.

The ECU <NUM> may be configured to operate the EAD <NUM> to apply force to the steering system <NUM> based on an estimation of the force applied to the steering system <NUM> by mechanical dampers <NUM>. Specifically, the ECU <NUM> may be configured to determine a target force for the enhanced steering control system <NUM> to apply the steering system <NUM> based on the sensor data, to estimate the force being applied to the steering system <NUM> by the mechanical dampers <NUM> based on the sensor data, and to operate the EAD <NUM> to apply additional force to the steering system <NUM> that minimizes a difference between the force applied to the steering system <NUM> by the enhanced steering control system <NUM> and the target force based on the estimated force. Depending on the current operational state of the PWC <NUM> indicated by the sensor data, the ECU <NUM> may operate the EAD <NUM> to apply force to the steering system <NUM> that is in a same or opposite direction as the force being applied by the mechanical dampers <NUM> to acheive the target force. In either case, the force applied by the EAD <NUM> may supplement that applied by the mechanical dampers <NUM> to effect a target force being applied the steering system <NUM>, which may enable the size and power consumption of the EAD <NUM> to be reduced relative to if the enhanced steering control system <NUM> was implemented without the mechanical dampers <NUM>.

Referring to <FIG>, the ECU <NUM> may include a processor <NUM>, memory <NUM>, non-volatile storage <NUM>, and an input/output (I/O) interface <NUM>. The processor <NUM> may include one or more devices selected from microprocessors, micro-controllers, digital signal processors, microcomputers, central processing units, field programmable gate arrays, programmable logic devices, state machines, logic circuits, analog circuits, digital circuits, or any other devices that manipulate signals (analog or digital) based on operational instructions read from the non-volatile storage <NUM> and stored in memory <NUM>. The memory <NUM> may include a single memory device or a plurality of memory devices including, but not limited, to read-only memory (ROM), random access memory (RAM), volatile memory, non-volatile memory, static random access memory (SRAM), dynamic random access memory (DRAM), flash memory, cache memory, or any other device capable of storing information. The non-volatile storage <NUM> may include one or more persistent mass data storage devices such as a hard drive, optical drive, tape drive, non-volatile solid-state device, or any other device capable of persistently storing information.

The processor <NUM> may be configured to implement the functions, features, modules, processes, and methods of the ECU <NUM> described herein. In particular, the processor <NUM> may operate under control of software, such as an operating system <NUM> and a steering control application <NUM>, embodied by computer-executable instructions residing in the non-volatile storage <NUM>. The computer-executable instructions may be compiled or interpreted from a variety of programming languages and/or technologies, including, without limitation, and either alone or in combination, Java, C, C++, C#, Objective C, Fortran, Pascal, Java Script, Python, Perl, and PL/SQL. The processor <NUM> may be configured to execute the software by being configured to read into memory <NUM> and execute the computer-executable instructions embodying the software residing in the non-volatile storage <NUM>. The computer-executable instructions may be configured, upon execution of the processor <NUM>, to cause the processor <NUM> to implement the functions, features, modules, processes, and methods of the ECU <NUM> described herein. In this way, the software may be configured to implement the functions, feature, modules, processes, and methods of the ECU <NUM> described herein.

For example, the operating system <NUM> may be configured to manage computer resources so that the steering control application <NUM> may be executed by the processor <NUM>. Alternatively, the processor <NUM> may execute the steering control application <NUM> directly, in which case the operating system <NUM> may be omitted. The steering control application <NUM> may be configured to implement enhanced steering control for the PWC <NUM> by being configured to determine a target force for the enhanced steering control system <NUM> to apply the steering system <NUM> based on the sensor data, estimate the force applied to the steering system <NUM> by the mechanical dampers <NUM> based on the sensor data, and to operate the EAD <NUM> to apply additional force to the steering system <NUM> that minimizes a difference between the force applied to the steering system <NUM> by the enhanced steering system <NUM> and the target force based on the estimated force. Further details regarding these operations are provided below.

The non-volatile storage <NUM> may also include data, such as steering control data <NUM>, supporting the functions, features, modules, processes, and methods of the ECU <NUM> described herein. The software of the ECU <NUM>, such as the steering control application <NUM>, may be configured to access this data during execution. For instance, the steering control data <NUM> may include data modeling operation of the mechanical dampers <NUM> as a function of the operational state of the PWC <NUM>, data defining target forces for the enhanced steering control system <NUM> to apply to the steering system <NUM> as a function of the operational state of the PWC <NUM>, and data defining forces applied by the EAD <NUM> to the steering system <NUM> as a function of electrical current supplied to the motor <NUM>. The steering control application <NUM> may thus be configured to access the steering control data <NUM> to determine a target force for enhanced steering control system <NUM> to apply the steering system <NUM> based on the sensor data, estimate the force applied to the steering system <NUM> by the mechanical dampers <NUM> based on the sensor data, and to operate the EAD <NUM> to apply the additional force to the steering system <NUM>.

The ECU <NUM> may be operatively coupled to one or more external resources <NUM> via the I/O interface <NUM>. The I/O interface <NUM> may include one or more wireless interfaces such as Wi-Fi and Bluetooth, and may include one or more wired interfaces such as Ethernet and CAN. The external resources <NUM> may include one or more other components of the PWC <NUM>, such as the EAD <NUM> and the sensors <NUM>.

While an exemplary PWC <NUM> is illustrated in <FIG> and <FIG>, the example is not intended to be limiting. Indeed, the PWC <NUM> may have more or fewer components, and alternative components and/or implementations may be used. For instance, the described functions of two or more of the above-described components may be combined and implemented by a single component, and the described functions of one of the above-described components may be implemented across several components. As an example, the illustrated ECU <NUM> may be implemented by multiple ECUs that are configured to cooperatively implement the functionality of the ECU <NUM> described herein.

<FIG> illustrates an example of the enhanced steering control system <NUM>. As shown in the illustrated example, the enhanced steering control system <NUM> may be provided as a single unit or device adapted to be coupled to the steering system <NUM>. Specifically, the enhanced steering control system <NUM> may include a housing <NUM> encompassing the EAD <NUM>, ECU <NUM>, one or more of the sensors <NUM>, mechanical dampers <NUM>, and a portion of the motor shaft <NUM>. The motor shaft <NUM> may extend from the housing <NUM> and be adapted to be coupled to the steering column <NUM>, either directly or through the gearbox <NUM>. The one or more of the sensors <NUM> may be arranged within the housing <NUM> adjacent the motor shaft <NUM> so as to generate the above-described sensor data based on rotation of the motor shaft <NUM>, which may correspond to the rotation of the steering system <NUM>. The mechanical dampers <NUM> may also be arranged within the housing <NUM> so as to be adjacent and coupled to the motor shaft <NUM>. During operation of the PWC <NUM>, the mechanical dampers <NUM> may apply force to the steering system <NUM> as described above by applying corresponding force to the motor shaft <NUM>, which may be coupled to and rotate with the steering system <NUM>.

<FIG> illustrates a method <NUM> for implementing enhanced steering control in a recreational vehicle such as a PWC <NUM>. The ECU <NUM> may be configured to perform or implement the method <NUM>, such as via execution of the steering control application <NUM>.

In block <NUM>, a force may be received by the steering system <NUM>. For instance, a driver may rotate the steering handle <NUM> and thereby apply a torque to the steering system <NUM>, or more particularly to the steering column <NUM>, such as to effect a turn. Environmental conditions may also place a torque on the steering system <NUM>. For instance, large waves and high speed winds may cause movement of the nozzle <NUM>, which may correspondingly apply a torque to the steering column <NUM> and the steering handle <NUM>.

In block <NUM>, a current operational state of the PWC <NUM> may be determined, such as based on the sensor data generated by the one or more sensors <NUM>. The ECU <NUM> may be configured to determine the current operational state of the PWC <NUM>, which may be defined by values for one or more operational parameters of the PWC <NUM>, based on the sensor data. For instance, the ECU <NUM> may be configured to determine a current angle of the steering system <NUM> based on the sensor data generated by the steering angle sensor, as described above. The ECU <NUM> may also be configured to determine a current steering rate of the steering system <NUM> based on the sensor data as described above. In some examples, the angle of the steering system <NUM> and the steering rate may be the only operational parameters defining the operational state of the PWC <NUM> determined by the ECU <NUM> in block <NUM>.

Alternatively, one or more other operational parameters may also or instead define the operational state of the PWC <NUM> determined by the ECU <NUM> in block <NUM>. For instance, the ECU <NUM> may be configured to determine a current torque on the steering system <NUM> based on sensor data generated by the steering torque sensor, a current rotational speed of the engine <NUM> and/or turbine <NUM> based on sensor data generated by the rotation sensor, a current extent of throttle actuation based on sensor data generated by the throttle request sensor, a current speed of the PWC <NUM> based on sensor data generated by the speed sensor or navigation system, a current position of the PWC <NUM> based on sensor data generated by the navigation system, a current heading of the PWC <NUM> based on sensor data generated by the navigation system, and/or a current acceleration level of the PWC <NUM> based on sensor data generated by the one or more of the sensors <NUM> as described above. The ECU <NUM> may thus be configured to determine the current operational state of the of the PWC <NUM> from the sensor data by being configured to determine values for one or more of the above operational parameters, the current angle of the steering system <NUM>, and/or the current steering rate of the steering system <NUM>.

In block <NUM>, a target torque for the steering system <NUM> may be determined based on the operational state of the PWC <NUM>. The target torque may be a torque desired to be applied to the steering system <NUM> by the enhanced steering control system <NUM>, or more particularly by the mechanical dampers <NUM> and the EAD <NUM>, to provide the PWC <NUM> with enhanced steering control. The direction of the target torque may depend on the enhanced steering control function being provided. The ECU <NUM> may be configured to determine the target torque based on the determined operational state of the PWC <NUM> and the steering control data <NUM>. The steering control data <NUM> may include data associating varying possible operational states with different target torques in accordance with desired enhanced steering controls, such as through one or more formulas and/or lookup tables defined by the steering control data <NUM>.

As an example, for each of one or more of the operational parameters defining the current operational state of the PWC <NUM>, the steering control data <NUM> may associate varying possible values for the operational parameter with different torque values. Given a current operational state of the PWC <NUM> including a particular value for each of these one or more operational parameters, the ECU <NUM> may be configured to determine the target torque by being configured to determine the torque value associated with each particular value in the steering control data <NUM>, to determine a base torque for the enhanced steering control system <NUM> based on each determined torque value, and to then determine the target torque based on the base torque. If there is only one determined torque value, then the ECU <NUM> may be configured to use this torque value as the base torque. If there is more than one determined torque value, then the ECU <NUM> may be configured to determine the base torque by summing the determined torque values, multiplying the magnitudes of the determined torque values, determining an average of the determined torque values, or using the determined torque value with the highest magnitude as the base torque. In some examples, the ECU <NUM> may be configured to use the determined base torque as the target torque determined in block <NUM>.

Alternatively, for each of one or more operational parameters defining the operational state of the PWC <NUM>, the steering control data <NUM> may also associate varying possible values for the operational parameter with different weight values. Given a current operational state of the PWC <NUM> including a particular value for each of these one or more operational parameters, the ECU <NUM> may be configured to determine the weight value associated with each particular value in the steering control data <NUM>, to determine a base weight for the enhanced steering control system <NUM> based on each determined weight value, and to then determine the target torque based on the base weight and the base torque described above. If there is only one determined weight value, then the ECU <NUM> may be configured to use this weight value as the base weight. If there is more than one determined weight value, then the ECU <NUM> may be configured to determine the base weight by summing the determined weight values, multiplying the magnitudes of the determined torque values, determining an average of the determined weight values, or using the highest determined weight value as the base weight. The ECU <NUM> may be configured to determine the target torque by multiplying the base weight by the base torque. The one or more operational parameters associated with torque values in the steering control data <NUM> may differ from the one or more operational parameters associated with weight values in the steering control data <NUM>.

As a further alternative, the ECU <NUM> may be configured to determine the target torque in block <NUM> by directly multiplying the determined base torque described above by the current value for one or more of the operational parameters defining the current operational state of the PWC <NUM>. The one or more operational parameters associated with torque values in the steering control data <NUM> and contributing to the base torque may differ from the one or more operational parameters being directly multiplied. For instance, the current operational state of the PWC <NUM> may include a current angle of the steering system <NUM> and a current steering rate of the steering system <NUM>. In this case, the ECU <NUM> may be configured to determine the target torque in block <NUM> by determining the torque value associated with the current angle of the steering system <NUM> in the steering control data <NUM> as the base torque, and multiplying this base torque by the current steering rate of the steering system <NUM> to determine the target torque. The target torque may thus be proportional to the current steering rate of the steering system <NUM>.

The steering control data <NUM> may include a lookup table for an operational parameter defining the current operational state of the PWC <NUM> that omits an entry associating the current value for the operational parameter with a torque value or weight value. In this case, the ECU <NUM> may be configured to interpolate such an entry from two or more entries of the lookup table closest to the current value for the operational parameter. For instance, the ECU <NUM> may be configured to use linear interpolation to determine the missing entry. In some examples, the steering control data <NUM> may include at least one multi-dimensional lookup table associating varying possible combinations of values for operational parameters defining the operational state of the PWC <NUM> with different torque values or weight values. In this case, the ECU <NUM> may be configured to input the current values for these operational parameters into the lookup table to determine the torque value or weight value associated with the current values, and then determine the target torque as described above. The ECU <NUM> may be configured to similarly use multi-dimensional interpolation, such as multi-dimensional linear interpolation, to determine a torque value or weight value for a combination of current values omitted from the lookup table.

In one example, the determined target torque may be configured to resist rotation of the steering system <NUM>, or more particularly of the steering handle <NUM>, to provide increased steering feedback to the driver based on the current operational state of the PWC <NUM> and prevent intense environmental conditions from adjusting the angle of the steering system <NUM>. For instance, the current operational state of the PWC <NUM> may include a current steering angle and/or a current steering rate of the steering system <NUM>. The ECU <NUM> may be configured to determine a target torque that resists rotation of the steering system <NUM> based on the current steering angle and/or steering rate and the steering control data <NUM>. Specifically, the steering control data <NUM> may associate possible steering angles each with a different torque value, and/or may associated possible steering rates each with a different torque value or weight value. The ECU <NUM> may be configured to determine the target torque by determining the torque value associated with the current steering angle in the steering control data <NUM> and/or determining the torque value or weight value associated with the current steering rate of the steering system <NUM> in the steering control data <NUM>, and then determining the target torque based on each determined torque value and/or weight value as described above.

The steering control data <NUM> may be configured such that the greater the possible steering angle, the greater the magnitude of the torque value associated with the steering angle, and/or the greater the possible steering rate, the greater the magnitude of the torque value or weight value associated with the possible steering rate. Consequently, the greater the steering angle and/or steering rate, the greater the magnitude target torque. The determined target torque may include a direction towards the center position of the steering system <NUM>, or may include a direction opposite the direction of rotation of the steering system <NUM>, which may be indicated by the sign of the steering rate as described above.

The ECU <NUM> may further be configured to determine a target torque for resisting rotation of the steering system <NUM> based on additional operational parameters, such as the current speed, engine RPM value, throttle request extent, and/or acceleration level indicated in the current operational state of the PWC <NUM>. For instance, the steering control data <NUM> may associate possible speeds, possible engine RPM values, possible throttle request extents and/or acceleration levels each with a different weight value. The ECU <NUM> may be configured to determine the target torque that resists rotation of the steering system <NUM> by determining the weight value associated with the current speed, engine RPM value, and/or throttle request value of the PWC <NUM> in the steering control data <NUM>, and determining the target torque based on each determined weight value and the base torque as described above. The steering control data <NUM> may be configured such that the greater the possible value for each of the speed, engine RPM, throttle request extent, and/or acceleration level parameters, the greater the weight value associated with the possible value. Consequently, the greater the speed, engine RPM value, throttle request extent and/or acceleration level of the PWC <NUM>, the greater the target torque. In some instances, the ECU <NUM> may be configured to determine the target torque by multiplying the determined base torque by the current speed, engine RPM value, throttle request extent and/or acceleration level.

The determined target torque may also be configured to provide a self-centering function for the steering system <NUM>. For instance, the current operational state of the PWC <NUM> may include a current steering angle and a current steering rate of the PWC <NUM>, and the ECU <NUM> may be configured to determine a target torque providing a self-centering function based on the current steering angle, the current steering rate, and the steering control data <NUM>. Specifically, the ECU <NUM> may be configured to determine whether the current steering rate is less than a defined threshold, indicating the steering system <NUM> is not in substantial motion. Responsive to determining that the current steering rate is less than the defined threshold, the ECU <NUM> may be configured to determine a difference between the current steering angle of the steering system <NUM> and the center position for the steering system <NUM>. The steering control data <NUM> may associate possible differences between the steering angle and center position of the steering system <NUM> each with a different torque value for minimizing the difference. The ECU <NUM> may be configured to determine the target torque by determining the torque value associated with the determined difference in the steering control data <NUM>, and using the determined torque value, which may also be set as the base torque described above, as the target torque. The steering control data <NUM> may be configured such that the greater the possible difference, the greater the magnitude of the torque value associated with the possible difference so as to provide fast centering while minimizing steering overshoots. The determined target torque may include a direction towards the center position of the steering system <NUM>.

The ECU <NUM> may further be configured to determine a target torque for centering the steering system <NUM> based on additional operational parameters, such as the current speed, engine RPM value, throttle request extent, and/or acceleration level indicated in the current operational state of the PWC <NUM>. To this end, the steering control data <NUM> may associate possible speeds, possible engine RPM values, possible throttle request extents, and/or possible acceleration levels of the PWC <NUM> each with a different weight value. The ECU <NUM> may be configured to determine the target torque for centering the steering system <NUM> by determining the weight value associated with the current speed, engine RPM value, throttle request extent, and/or acceleration level of the PWC <NUM> in the steering control data <NUM>, and determining the target torque based on each determined weight value and a base torque as described above. The steering control data <NUM> may be configured such that the greater the possible value for each of the speed, engine RPM, throttle request extent, and/or acceleration level operational parameters, the greater the weight value associated with the possible value. In some instances, the ECU <NUM> may be configured to determine the target torque by multiplying the determined base torque by the current speed, engine RPM value, throttle request extent and/or acceleration level. Consequently, the greater the speed, engine RPM value, throttle request extent, and/or acceleration level of the PWC <NUM>, the greater the magnitude of the target torque so as to provide fast centering while minimizing steering overshoots.

The target torque may also be configured to provide a heading assist function for the steering system <NUM>. For instance, the current operational state of the PWC <NUM> may indicate a current heading of the PWC <NUM>, and the driver may interact with a navigation system of the PWC <NUM> to set a desired heading of the PWC <NUM>. The ECU <NUM> may be configured to determine a target torque for maintaining the set heading by determining a difference between the current heading of the PWC <NUM> and the set heading. The steering control data <NUM> may associate various possible differences between the current heading and set heading each with a different torque value for minimizing the difference. The ECU <NUM> may be configured to determine the target torque by determining the torque value associated with the determined difference in the steering control data <NUM>, and using the determined torque value, which may be set as the base torque described above, as the target torque. The determined target torque may include a direction that steers the PWC <NUM> from the current heading to the set heading. The steering control data <NUM> may be configured such that the greater the possible difference, the greater the magnitude of the torque value associated with the possible difference. Consequently, the greater the possible difference, the greater the magnitude of the target torque so as to provide fast heading adjustments while minimizing steering overshoots.

Similar to the above examples, the ECU <NUM> may further be configured to determine the target torque for adjusting the heading of the PWC <NUM> based on additional operational parameters, such as the current speed, engine RPM value, throttle request extent, and/or acceleration level indicated in the current operational state of the PWC <NUM>. To this end, the steering control data <NUM> may associate possible speeds, possible engine RPM values, possible throttle request extents, and/or possible acceleration levels of the PWC <NUM> each with a different weight value. The ECU <NUM> may be configured to determine the target torque for maintaining the set heading by determining the weight value associated with the current speed, engine RPM value, throttle request extent, and/or acceleration level of the PWC <NUM> in the steering control data <NUM>, and determining the target torque based on each determined weight value and an base torque as described above. The steering control data <NUM> may be configured such that the greater the possible value for each of the speed, engine RPM, throttle request extent, and/or acceleration level operational parameters, the greater the weight value associated with the possible value. In some instances, the ECU <NUM> may be configured to determine the target torque by multiplying the determined base torque by the current speed, engine RPM value, throttle request extent and/or acceleration level. Consequently, the greater the speed, engine RPM value, In some instances, the ECU <NUM> may be configured to determine the target torque by multiplying the determined base torque by the current speed, engine RPM value, throttle request extent and/or acceleration level of the PWC <NUM>, the greater the magnitude of the target torque so as to provide fast heading adjustments while minimizing steering overshoots.

The ECU <NUM> may thus be configured to determine a target torque for the enhanced steering control system <NUM> to apply to the steering system <NUM> by applying the current operational state of the PWC <NUM> to the steering control data <NUM>. In block <NUM>, the torque being applied to the steering system <NUM> by the mechanical dampers <NUM> may be estimated. In particular, the ECU <NUM> may be configured to estimate the torque force being applied to the steering system <NUM> by the mechanical dampers <NUM> based on the determined operational state of the PWC <NUM> and the steering control data <NUM>. Similar to the target torque examples provided above, and as described in more detail below, the steering control data <NUM> may include data associating varying possible operational states with different estimated torque forces applied by the mechanical dampers <NUM> to the steering system <NUM>, such as through one or more formulas and/or lookup tables defined by the steering control data <NUM>. The ECU <NUM> may thus be configured to estimate the torque force being applied to the steering system <NUM> by the mechanical dampers <NUM> by applying the current operational state of the PWC <NUM> to the steering control data <NUM>.

In block <NUM>, an additional torque to apply to the steering system <NUM> by the EAD <NUM> may be determined based on the estimated torque and the target torque. The ECU <NUM> may be configured to determine the additional torque based on the estimated torque and the target torque by being configured to determine a difference between the estimated torque and the target torque. The ECU <NUM> may be configured to use this difference as the additional torque. In other words, the ECU <NUM> may be configured to determine an additional torque to apply to the steering system <NUM> that supplements the estimated torque provided by the mechanical dampers <NUM> so that the combination of estimated torque and the additional torque results in the target torque being applied to the steering system <NUM>. For instance, if the estimated torque is less than and in the same direction as the target torque, then the additional torque may be in the direction of the estimated torque. If the estimated torque is greater than and in the same direction as the target torque, then the additional torque may be in the direction opposite of the estimated torque. If the estimated torque is in a direction opposite the target torque, then the additional torque may include a magnitude greater than that of the estimated torque and be in a direction opposite the estimated torque.

In block <NUM>, the EAD <NUM> may be operated to apply the additional torque to the steering system <NUM>. The ECU <NUM> may be configured to apply a current to the motor <NUM> of the EAD <NUM> that causes the motor <NUM> to apply the additional torque to the steering system <NUM>. The ECU <NUM> may be configured to determine the current for the motor <NUM> based on the steering control data <NUM>. The steering control data <NUM> may include data associating various torque forces for the steering system <NUM> each with a different electrical current value for the motor <NUM> to apply the torque force to the steering system <NUM>, such as through one or more formulas and/or lookup tables defined by the steering control data <NUM>. The ECU <NUM> may thus be configured to determine a current to apply to the motor <NUM> by applying the determined additional torque force to the steering control data <NUM>.

Following block <NUM>, the method <NUM> may return to block <NUM> and be repeated. The ECU <NUM> may thus be configured to perform a continuous loop during operation of the PWC <NUM> in which, for each iteration of the loop, the ECU <NUM> determines a current operational state of the PWC <NUM>, determines a target force for the steering system <NUM> based on the operational state, estimates a torque being applied to the steering system <NUM> by the mechanical dampers <NUM> based on the operational state, and operates the EAD <NUM> to apply additional torque to the steering system <NUM> based on the target torque, the estimated torque, and the operational state of the PWC <NUM>. During each iteration, the ECU <NUM> may also be configured to implement one or more proportional, integral, derivative (PID) algorithms to promote efficient enhanced steering control function and prevent steering overshoots.

<FIG> illustrates a linear model <NUM> for estimating the torque force applied to the steering system <NUM> by the mechanical dampers <NUM> based on a determined operational state of the PWC <NUM>. The steering control data <NUM> may indicate the linear model <NUM>. To perform block <NUM> of <FIG>, the ECU <NUM> may be configured, such as via execution of the steering control application <NUM>, to retrieve the linear model <NUM> from the steering control data <NUM>, and to apply the determined operational state of the PWC <NUM> to the linear model <NUM> to estimate the torque force applied to the steering system <NUM> by the mechanical dampers <NUM>.

The linear model <NUM> may model the torque force applied to the steering system <NUM> by each mechanical damper <NUM> as being linearly related to one or more of the operational parameters defining the current operational state of the PWC <NUM>. For instance, the torque force applied by the spring type mechanical damper 128A to the steering system <NUM> may be modeled as linearly related to a steering angle <NUM> of the steering system <NUM>, and the torque force applied by the fluid type mechanical damper 128B and the friction type mechanical damper 128C may be modeled as linearly related to a steering rate <NUM> of the steering system <NUM>.

For each mechanical damper <NUM>, the linear model <NUM> may include deadband data <NUM>, gain data <NUM>, and saturation data <NUM>. The deadband data <NUM> may indicate when the mechanical damper <NUM> begins applying torque to the steering system <NUM> as a function of the one or more operational parameters linearly related to the mechanical damper <NUM>. Specifically, each mechanical damper <NUM> may be configured to begin applying torque to the steering system <NUM> when the magnitude of at least one of the one or more operational parameters linearly related to the mechanical damper <NUM> is greater than a defined threshold. If the magnitude of all of the linearly related operational parameters are less than or equal to respectively defined thresholds, then the mechanical damper <NUM> may be configured to apply negligible (e.g., little or no) torque to the steering system <NUM>. The deadband data <NUM> for each mechanical damper <NUM> may thus define a deadband threshold for each of the one or more operational parameters linearly related to the mechanical damper <NUM>. For instance, the deadband data <NUM> may define a single deadband threshold for all the linearly related operational parameters, or may define a distinct deadband threshold for each of the linearly related operational parameters.

The ECU <NUM> may thus be configured to estimate the torque applied by each of the mechanical dampers <NUM> to the steering system <NUM> based on the linear model <NUM> by being configured to apply the current operational state of the PWC <NUM> to the deadband data <NUM> for the mechanical damper <NUM>. Specifically, for each operational parameter of the determined operational state that is linearly related to the mechanical damper <NUM>, the ECU <NUM> may be configured to determine whether the magnitude of the operational parameter included in the determined operational state is less than or equal to the deadband threshold for the operational parameter defined by the deadband data <NUM> for the mechanical damper <NUM>. Responsive to the magnitude of the operational parameter being less than or equal to the defined deadband threshold, the ECU <NUM> may be configured to output a base value of zero for the operational parameter relative to the mechanical damper <NUM>, indicating that the mechanical damper <NUM> is applying negligible torque to the steering system <NUM> as a function of the operational parameter.

Conversely, responsive to the magnitude of the operational parameter being greater than the defined deadband threshold, the ECU <NUM> may be configured to output a non-zero base value for the operational parameter relative to the mechanical damper <NUM>, indicating that the mechanical damper <NUM> is applying non-negligible torque to the steering system <NUM> as a function of the operational parameter. The magnitude of the non-zero base value may be proportional to the magnitude of the operational parameter according to a generic linear response for the mechanical damper <NUM>, which may define a slope such as one. The ECU <NUM> may be configured to determine the non-zero base value as equal to the difference between the magnitude of the operational parameter and the threshold defined for the operational parameter multiplied by the slope of the generic linear response.

The sign of the non-zero base value may correspond to the direction of the torque being applied by the mechanical damper <NUM> to the steering system <NUM>, and may be opposite the sign of the operational parameter. For instance, if the steering angle <NUM> is positive, which may indicate that the steering system <NUM> is positioned clockwise relative to its center position, then the ECU <NUM> may be configured to generate a negative non-zero base value for the steering angle operational parameter, which may correspond to the mechanical damper <NUM> applying torque to the steering system <NUM> towards the center position. As a further example, if the steering rate <NUM> is positive, which may indicate the steering system <NUM> is being rotated in the clockwise direction, then the ECU <NUM> may be configured to generate a negative non-zero base value for the steering rate operational parameter, which may correspond to the mechanical damper <NUM> applying torque to the steering system <NUM> in a direction opposite the current movement of the steering system <NUM>.

The ECU <NUM> may be configured to determine an effective base value for the mechanical damper <NUM> based the base values determined for each operational parameter linearly related to the mechanical damper <NUM>. The effective base value may indicate a direction and magnitude of torque that would be estimated for a generic mechanical damper that is of the same type as the mechanical damper <NUM>. The ECU <NUM> may be configured to determine the effective base value by summing the determined base values, multiplying the magnitudes of the determined based values, determining an average of the determined base values, or using the determined base value with the highest magnitude as the effective base value. The sign of the effective base value may correspond to the sign of each determined base value, and may similarly indicate the direction of the torque estimated to be applied by the mechanical damper <NUM>. Hence, if each of the determined base values is zero, then the effective base value determined for the mechanical damper <NUM> may be zero, indicating that the mechanical damper <NUM> is overall applying negligible torque to the steering system <NUM>. Moreover, if the mechanical damper <NUM> is linearly related to a single operational parameter, then the base value determined for this operational parameter may be used as the effective base value for the mechanical damper <NUM>.

Referring still to <FIG> as an example, if the steering angle <NUM> indicates that the distance between the current angle of the steering system <NUM> and a center position of the steering system <NUM> is less than or equal to a deadband threshold defined by deadband data 356A for the spring type mechanical damper 128A, then the ECU <NUM> may be configured to determine an effective base value of zero for the spring type mechanical damper 128A and ultimately, as described in more detail below, an estimated torque of zero being applied by the spring type mechanical damper 128A. Alternatively, if the steering angle <NUM> indicates that the distance between the current angle of the steering system <NUM> and the center position of the steering system <NUM> is greater than the defined deadband threshold, then the ECU <NUM> may be configured to determine a non-zero effective base value for the mechanical damper <NUM> that is proportional to the difference according to a generic linear response, such as a slope of one.

The gain data <NUM> for each mechanical damper <NUM> may indicate a level of torque applied to the steering system <NUM> by the specific mechanical damper <NUM> as a function of the magnitude of the one or more operational parameters linearly related to the mechanical damper <NUM>, or more particularly as a function of the effective base value for the mechanical damper <NUM>. Depending on the configuration of the mechanical damper <NUM>, its actual linear response may differ from the generic linear response. For instance, referring to the spring type mechanical damper 128A, the greater the stiffness of the spring type mechanical damper 128A, the more torque the spring type mechanical damper 128A may apply to the steering system <NUM> with each incremental increase to the steering angle <NUM>. Accordingly, for relatively stiffer spring type mechanical dampers 128A, the gain data 358A may define a gain parameter set to a relatively high value (e.g., ten) to model a linear response with a slope ten times greater than the slope of the generic linear response previously applied.

For each mechanical damper <NUM>, the ECU <NUM> may thus be configured to multiply the effective base value determined for the mechanical damper <NUM> by the gain parameter defined by the gain data <NUM> for the mechanical damper <NUM>. If the effective base value determined from the deadband data <NUM> is zero, which corresponds to the mechanical damper <NUM> providing negligible torque to the steering system <NUM>, then the outcome of the multiplication will similarly be zero. If the effective base value determined from the deadband data <NUM> is non-zero, then the outcome of the multiplication will be non-zero in accordance with the linear response set by the gain parameter defined by the gain data <NUM>.

The saturation data <NUM> for each mechanical damper <NUM> may define a maximum torque that the mechanical damper <NUM> is capable of applying to the steering system <NUM>. Each mechanical damper <NUM> may be limited in the amount of torque it is able to provide to the steering system <NUM>. The saturation data <NUM> may indicate this maximum torque.

The ECU <NUM> may thus be configured to estimate the amount of torque applied to the steering system <NUM> by each mechanical damper <NUM> by being configured to apply the result of the multiplication by the gain parameter for the mechanical damper <NUM> to the saturation data <NUM> for the mechanical damper <NUM>. Specifically, the ECU <NUM> may be configured to determine whether the magnitude of the result of the multiplication is greater than the maximum torque indicated by the saturation data <NUM>. Responsive to the magnitude of the multiplication result being less than or equal to the maximum torque indicated by the saturation data <NUM>, then the ECU <NUM> may be configured to estimate that the torque applied by the mechanical damper <NUM> to the steering system has a magnitude equal to the magnitude of the multiplication result. Responsive to the magnitude of the multiplication result being greater than the maximum torque defined by the saturation data <NUM>, then the ECU <NUM> may be configured to estimate the defined maximum torque as the magnitude of torque being applied by the mechanical damper <NUM> to the steering system <NUM>. The sign (i.e., direction) of the torque estimated as being applied to the steering system <NUM> by the mechanical damper <NUM> may match the sign of the effective base value and of the multiplication result.

Finally, the ECU <NUM> may be configured to determine an estimated torque <NUM> being applied to the steering system <NUM> by the mechanical dampers <NUM> based on the estimated torque being applied by each mechanical damper <NUM>. The ECU <NUM> may be configured to determine the estimated torque <NUM> by performing a summation <NUM> of the estimated torque determined for each mechanical damper <NUM>.

<FIG> illustrates a non-linear model <NUM> for estimating the torque force applied to the steering system <NUM> by the mechanical dampers <NUM> based on the determined operational state of the PWC <NUM>. The steering control data <NUM> may indicate the non-linear model <NUM>. To perform block <NUM> of <FIG>, the ECU <NUM> may be configured, such as via execution of the steering control application <NUM>, to retrieve the non-linear model <NUM> from the steering control data <NUM>, and to apply the determined operational state of the PWC <NUM> to the non-linear model <NUM> to estimate the torque applied to the steering system <NUM> by the mechanical dampers <NUM>.

The amount of torque applied to the steering system <NUM> by each mechanical damper <NUM> may be a function of one or more operational parameters defining the current operational state of the PWC <NUM>. The relationship between the operational parameters and applied torque may be non-linear. Thus, for each mechanical damper <NUM>, the non-linear model <NUM> may include a one dimensional (1D) table <NUM> or a multi-dimensional table defining different possible parameter states each including a possible value for each of the one or more operational parameters to which the mechanical damper <NUM> is functionally related, and associating each possible parameter state with a corresponding torque estimated to be applied to the steering system <NUM> by the mechanical damper <NUM> when the determined operational state of the PWC <NUM> includes the one or more possible values of the possible parameter state. Specifically, when the response of the mechanical damper <NUM> is a function of one operational parameter, the non-linear model <NUM> may define a 1D table <NUM> for the mechanical damper <NUM>. When the response of the mechanical damper <NUM> is a function of plural operational parameters, the non-linear model <NUM> may define a multi-dimensional table for the mechanical damper <NUM>, where the number of dimensions equals the number of associated operational parameters.

For instance, referring to <FIG>, the amount torque provided by the spring type mechanical damper 128A may be a function of the steering angle <NUM> of the PWC <NUM>, and the amount of torque provided by the fluid type mechanical damper 128B and the friction type mechanical damper 128C may each be a function of the steering rate <NUM> of the steering system <NUM>. Thus, the non-linear model <NUM> may define a 1D table <NUM> for each mechanical damper <NUM>. The 1D table 402A for the spring type mechanical damper 128A may set forth various possible steering angles <NUM>, and may associate each possible steering angle <NUM> with a torque applied to the steering system <NUM> by the spring type mechanical damper 128A when the current operational state of the PWC <NUM> indicates the possible steering angle <NUM>. Similarly, the 1D tables 402B and 402C for the fluid type mechanical damper 128B and friction type mechanical damper 128C respectively may each set forth various possible steering rates <NUM>, and may each associate each possible steering rate <NUM> with a torque applied to the steering system <NUM> by the fluid type mechanical damper 128B and friction type mechanical damper 128C respectively when the current operational state of the PWC <NUM> indicates the possible steering rate <NUM>.

The ECU <NUM> may be configured to estimate the amount of torque applied to the steering system <NUM> by the mechanical dampers <NUM> using the non-linear model <NUM> by being configured to apply the determined operational state of the PWC <NUM> to the defined tables, such as the 1D tables <NUM>. Specifically, the ECU <NUM> may be configured to estimate the amount of torque applied by each mechanical damper <NUM> by being configured to apply the values for the one or more operational parameters to which the mechanical damper <NUM> is functionally related and indicated in the current operational state of the PWC <NUM> to the 1D table <NUM> or multi-dimensional table for the mechanical damper <NUM> in the non-linear model <NUM>. If the one or more applied operational parameter values matches one of the possible parameter states set forth in the table (e.g., is equivalent to or within a threshold distance, such as based on a sum of squared distances between corresponding values), then the ECU <NUM> may be configured to estimate that the torque associated with the matched possible parameter state in the table is being applied to the steering system <NUM> by the mechanical damper <NUM>. If not, then the ECU <NUM> may be configured to utilize interpolation, such as linear interpolation, to estimate the torque applied to the steering system <NUM> by the mechanical damper <NUM>. For instance, the ECU <NUM> may be configured to interpolate the estimated torque based on the two or more possible parameters states in the table that are closest to or surrounding the current operational state, which may be determined using the sum of squared distances between corresponding values.

Finally, the ECU <NUM> may be configured to determine an estimated torque <NUM> being applied to the steering system <NUM> by the mechanical dampers <NUM> based on the estimated torque being applied by each mechanical damper <NUM>. For instance, the ECU <NUM> may be configured to determine the estimated torque <NUM> by performing a summation <NUM> of the estimated torque applied by each mechanical damper <NUM>. The sign of the estimated torque <NUM> may correspond to the direction of the torque being applied to the steering system <NUM> by the mechanical dampers <NUM>.

<FIG> illustrates another non-linear model <NUM> for estimating the force applied to the steering system <NUM> by the mechanical dampers <NUM> based on the determined operational state of the PWC <NUM>. The steering control data <NUM> may indicate the non-linear model <NUM>. To perform block <NUM> of <FIG>, the ECU <NUM> may be configured, such as via execution of the steering control application <NUM>, to retrieve the non-linear model <NUM> from the steering control data <NUM>, and to apply the determined operational state of the PWC <NUM> to the non-linear model <NUM> to estimate the torque applied to the steering system <NUM> by the mechanical dampers <NUM>.

In the example of <FIG>, the mechanical dampers <NUM> of the PWC <NUM> includes a spring type mechanical damper 128A and a fluid type mechanical damper 128B that is a MR fluid damper. The torque applied by the spring type mechanical damper 128A to the steering system <NUM> may be a function of the steering angle <NUM> of the PWC <NUM>, and the force applied by the MR fluid type mechanical damper 128B to the steering system <NUM> may be a function of the steering rate <NUM> of the PWC <NUM> and an MR control state <NUM>. The MR control state <NUM> may indicate the characteristics of a magnetic field being applied to the MR fluid type mechanical damper 128B, which may correspondingly indicate which of possible responses will be provided by the fluid type mechanical damper 128B as a function of the steering rate <NUM>.

In this case, the non-linear model <NUM> may include a 1D table 402A for the spring type mechanical damper 128A, which is described above, and may include a two-dimensional (2D) table 402D for the MR fluid type mechanical damper 128B. The 2D table 402D may define several different possible parameter states each including a different combination of possible values for the steering rate <NUM> and MR control state <NUM>, and may associate each possible parameter state with a torque estimated to be applied by the MR fluid type mechanical damper 128B when the current operational state of the PWC <NUM> includes the possible values of the possible parameter state. Essentially, the 2D table 402D may be considered as including several fluid 1D tables 402B (<FIG>), each representing a possible response of the MR fluid type mechanical damper 128B as a function of the steering rate <NUM> depending on the current MR control state <NUM>. In other words, each of the 1D tables 402B indicated by the 2D table 402D for the MR fluid type mechanical damper 128B may be associated with a different possible MR control state <NUM>.

The ECU <NUM> may be configured to estimate the amount of torque applied to steering system <NUM> by the mechanical dampers <NUM> using the non-linear model <NUM> by applying the current operational state of the PWC <NUM> to the 1D table 402A for the spring type mechanical damper 128A and the 2D table 402D for the MR fluid type mechanical damper 128B. Specifically, the ECU <NUM> may be configured to estimate the amount of torque being applied by the spring type mechanical damper 128A to the steering system <NUM> by applying the steering angle <NUM> indicated by the current operational state of the PWC <NUM> to the 1D table 402A, and may be configured to estimate the amount of torque being applied to the steering system <NUM> by the MR fluid type mechanical damper 128B by applying the steering rate <NUM> and MR control state <NUM> indicated by the current operational state of the PWC <NUM> to the 2D table 402D. If the one or more operational parameter values applied to each table match a possible parameter state of the table (e.g., is equivalent to or within a threshold distance of a possible parameter state of the table, such as based on a sum of squared distances of corresponding values), then the ECU <NUM> may be configured to estimate the torque associated with the matching possible parameter state within the table as the torque being applied by the mechanical damper <NUM>. If the one or more operational parameter values applied to a given table do not match a possible parameter state of the table, then the ECU <NUM> may be configured to estimate a torque provided by the mechanical damper <NUM> associated with the table using interpolation, such as linear interpolation for the spring 1D table 402A and bilinear interpolation for the 2D table <NUM>.

In some examples, a combination of linear and non-linear models may be used to model the force applied by the mechanical dampers <NUM> on the steering system <NUM> as a function of the operational state of the PWC <NUM>. Specifically, one or more of the mechanical dampers <NUM> may be modeled as being linearly related to one or more operational parameters, similar to the linear model <NUM>, and one or more of the mechanical dampers <NUM> may be modeled as being non-linearly related to one or more operational parameters, similar to the non-linear models <NUM>, <NUM>. The steering control data <NUM> may store the model for each of the mechanical dampers <NUM>, whether linear or non-linear. To perform block <NUM> of <FIG>, the ECU <NUM> may be configured, such as via execution of the steering control application <NUM>, to retrieve the models from the steering control data <NUM>, and to apply the relevant operational parameters of the determined operational state of the PWC <NUM> to each model to estimate the torque force applied to the steering system <NUM> by the mechanical dampers <NUM> associated with the model. The ECU <NUM> may be configured to then sum the torque force estimated for each mechanical damper <NUM> to determine a total estimated torque force applied to the steering system <NUM> by the mechanical dampers <NUM>.

While the enhanced steering control system <NUM>, method <NUM>, and other features have been described above in connection with a PWC, it will be appreciated that these items may be incorporated into other recreational vehicles to provide the enhanced steering control functionality described above. For instance, <FIG> illustrates a snowmobile <NUM> including a steering handle <NUM> and steering skis <NUM>, and <FIG> illustrates an all-terrain vehicle (ATV) <NUM> including a steering handle <NUM> and tires <NUM>. As described in more detail below, each of these recreational vehicle types may benefit from the enhanced steering control features described herein.

<FIG> illustrates an exemplary steering assembly <NUM> that may be incorporated into a recreational vehicle such as the snowmobile <NUM> and ATV <NUM>. The steering assembly <NUM> may include a user-operated steering element <NUM>, a steering column <NUM>, a steering rack <NUM>, steering rods <NUM>, and ground engaging members <NUM>. The steering column <NUM> may be coupled to and rotatable with the user-operated steering element <NUM>, which may be the steering handle <NUM> of the snowmobile <NUM> (<FIG>) or the steering handle <NUM> of the ATV <NUM> (<FIG>). The steering column <NUM> may also be coupled to the ground engaging members <NUM>, which may be the steering skis <NUM> of the snowmobile <NUM> (<FIG>) or the tires <NUM> of the ATV <NUM> (<FIG>), such as via the steering rack <NUM> and the steering rods <NUM>. Rotation of the user-operated steering element <NUM> may cause a corresponding rotation of the steering column <NUM>, which may cause a corresponding movement of the steering rods <NUM>, which in turn may cause corresponding turning of the ground engaging members <NUM> to steer the recreational vehicle.

According to the mechanical linkage provided by the steering assembly <NUM>, the ground engaging members <NUM> may be coupled to and rotatable with the user-operated steering element <NUM> such that rotation of the user-operated steering element <NUM> causes a corresponding rotation of the ground engaging members <NUM> to steering the vehicle. Similarly, the user-operated steering element <NUM> may be coupled to and rotatable with the ground engaging members <NUM> such that external environmental forces (e.g., moguls, off-road driving surfaces) acting on the ground engaging members <NUM> may be translated to a rotation of the steering column <NUM> and user-operated steering element <NUM>.

Like the steering system <NUM> of the PWC <NUM> described above, the steering assembly <NUM> may have a relatively small lock-to-lock range (e.g., less than ninety-degrees), which may offer very quick but low-resolution steering control when compared to the typical automobile. Moreover, relative to the automobile, each of these types of recreational vehicles may be operated over relatively harsh terrain, which may include steep and inconsistent elevations, moguls, slippery surfaces, and malleable surfaces that form tracks in various directions from the previous passage of other like vehicles. During operation of the snowmobile <NUM> or ATV <NUM>, such terrain may act on the ground engaging members <NUM>, and may correspondingly apply a torque to the steering assembly <NUM> that biases the vehicle in an unintended direction. The driver may reactively expend an exhaustive amount of effort to apply corrective torque to the steering assembly <NUM> that maintains the direction of the vehicle. The driver may also associate the difficulty of maintaining a direction of the vehicle with a lack of control, which may lead to the driver to perform dangerous maneuvers, such as oversteering at high speeds.

To alleviate these issues, the steering assembly <NUM> may be equipped with the enhanced steering control system <NUM> configured to operate as described above. Specifically, the enhanced steering control system <NUM> may be equipped with one or more mechanical dampers <NUM> that are coupled to and configured to provide resistive torque to the steering assembly <NUM>. The resistive torque may help limit the effect of harsh terrain on the steering assembly <NUM>, and may help prevent the driver from performing dangerous steering maneuvers.

As described above, the enhanced steering control system may further include one or more sensors <NUM>, an ECU <NUM>, and an EAD <NUM> that generates torque on the steering assembly <NUM> to supplement that provided by mechanical dampers <NUM> to provide desired enhanced steering control functionality. For instance and similar to the examples described above, based on operational parameters determined by the ECU <NUM> from sensor data such as the angle of the steering assembly <NUM>, the steering rate of the steering assembly <NUM>, the speed of the recreational vehicle, and the acceleration level of the recreational vehicle, the ECU <NUM> may be configured to determine a target torque for the steering assembly <NUM>, estimate a torque being applied by the mechanical dampers <NUM>, and operate the EAD <NUM> to apply additional torque to the steering assembly <NUM> that minimizes the difference between the target torque and actual torque on the steering assembly <NUM> based on the torque estimated as being applied by the mechanical dampers <NUM>. As an example, the target torque may be configured to increase or reduce the resistive torque provided to the steering assembly <NUM> from that provided by the mechanical dampers <NUM> to prevent undesired manipulation of the steering assembly <NUM> based on the current operating condition of the recreational vehicle determined by the ECU <NUM>. As a further example, the target torque may be configured to reduce the resistive torque provided to the steering assembly <NUM> from that provided by the mechanical dampers <NUM> so as to assist the driver in rotating the user-operating steering element <NUM> when the current operational state indicates that the driver is attempting to turn the vehicle, which may be derived from the sensor data generated by the torque sensor.

The lack of steering feedback and relatively quick low resolution steering control provided by a recreational vehicle such as a typical PWC may lead an unexperienced driver to perform dangerous maneuvers, such as excessive steering operations at high speeds that eject the driver from the PWC. A PWC <NUM> with enhanced steering control for providing increased steering feedback to a driver is therefore described herein. The enhanced steering control may utilize a combination of mechanical dampers <NUM> and an EAD <NUM> each configured to apply torque to the steering system of the PWC <NUM> that provides increased steering feedback to the driver. Utilizing both the EAD <NUM> with the mechanical dampers <NUM> to provide the enhanced steering control enables the PWC <NUM> to provide dynamic steering feedback based on the current operational state of the PWC <NUM> while reducing the size of the EAD <NUM> and the electrical load required to provide the desired steering feedback. The enhanced steering control systems and methods described herein may also benefit other recreational vehicle types, such as a snowmobile <NUM> or ATV <NUM>, which may incorporate the enhanced steering control systems and methods to provide the driver with improved steering control functionality.

In general, the routines executed to implement the embodiments of the invention, whether implemented as part of an operating system or a specific application, component, program, object, module or sequence of instructions, or even a subset thereof, may be referred to herein as "computer program code," or simply "program code. " Program code typically comprises computer readable instructions that are resident at various times in various memory and storage devices in a computer and that, when read and executed by one or more processors in a computer, cause that computer to perform the operations necessary to execute operations and/or elements embodying the various aspects of the embodiments of the invention. Computer readable program instructions for carrying out operations of the embodiments of the invention may be, for example, assembly language or either source code or object code written in any combination of one or more programming languages.

The program code embodied in any of the applications/modules described herein is capable of being individually or collectively distributed as a program product in a variety of different forms. In particular, the program code may be distributed using a computer readable storage medium having computer readable program instructions thereon for causing a processor to carry out aspects of the embodiments of the invention.

Computer readable storage media, which is inherently non-transitory, may include volatile and non-volatile, and removable and non-removable tangible media implemented in any method or technology for storage of information, such as computer-readable instructions, data structures, program modules, or other data. Computer readable storage media may further include RAM, ROM, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other solid state memory technology, portable compact disc read-only memory (CD-ROM), or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and which can be read by a computer. A computer readable storage medium should not be construed as transitory signals per se (e.g., radio waves or other propagating electromagnetic waves, electromagnetic waves propagating through a transmission media such as a waveguide, or electrical signals transmitted through a wire). Computer readable program instructions may be downloaded to a computer, another type of programmable data processing apparatus, or an0other device from a computer readable storage medium or to an external computer or external storage device via a network.

Computer readable program instructions stored in a computer readable medium may be used to direct a computer, other types of programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions that implement the functions/acts specified in the flowcharts, sequence diagrams, and/or block diagrams. The computer program instructions may be provided to one or more processors of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the one or more processors, cause a series of computations to be performed to implement the functions and/or acts specified in the flowcharts, sequence diagrams, and/or block diagrams.

In certain alternative embodiments, the functions and/or acts specified in the flowcharts, sequence diagrams, and/or block diagrams may be re-ordered, processed serially, and/or processed concurrently without departing from the scope of the invention. Moreover, any of the flowcharts, sequence diagrams, and/or block diagrams may include more or fewer blocks than those illustrated consistent with embodiments of the invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the embodiments of the invention. Furthermore, to the extent that the terms "includes", "having", "has", "with", "comprised of", or variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprising".

Claim 1:
An enhanced steering control system (<NUM>) for a steering system (<NUM>) of a recreational vehicle including one or more mechanical dampers (<NUM>) coupled to the steering system (<NUM>) that resist movement of the steering system (<NUM>), the enhanced steering control system (<NUM>) comprising:
an electrically actuated device (<NUM>) adapted to be coupled to the steering system (<NUM>) for applying force to the steering system (<NUM>);
a sensor (<NUM>) adapted to be positioned adjacent the steering system (<NUM>) when the electrically actuated device (<NUM>) is coupled to the steering system (<NUM>) that generates data indicating an operational state of the recreational vehicle; and
a controller (<NUM>) coupled to the electrically actuated device <NUM>) and the sensor (<NUM>) and configured to:
estimate a first torque applied to the steering system (<NUM>) by the one or more mechanical dampers (<NUM>) based on the operational state by being configured to:
apply the operational state to a model specific to each of the one or more mechanical dampers (<NUM>) to determine a third torque applied to the steering system (<NUM>) by the mechanical damper (<NUM>),
the model specific to each of the one or more mechanical dampers (<NUM>) including deadband data, a gain parameter, and saturation data for the mechanical damper,
the controller (<NUM>) determining the third torque applied to the steering system (<NUM>) by the mechanical damper (<NUM>) by being configured to:
generate a first value for the mechanical damper (<NUM>) based on the deadband data for the mechanical damper (<NUM>) and the operational state;
generate a second value for the mechanical damper (<NUM>) by multiplying the first value for the mechanical damper by the gain parameter for the mechanical damper; and
determine the third torque applied to the steering system (<NUM>) by the mechanical damper (<NUM>) based on the second value for the mechanical damper (<NUM>) and the saturation data for the mechanical damper (<NUM>); and
estimate the first torque applied to the steering system (<NUM>) by the one or more mechanical dampers (<NUM>) based on the third torque estimated for each of the one or more mechanical dampers (<NUM>);
calculate a second torque to apply to the steering system (<NUM>) by the electrically actuated device (<NUM>) based on the estimated first torque and the operational state; and
operate the electrically actuated device (<NUM>) to apply the second torque to the steering system (<NUM>).