Patent Application
20130073157
The present invention relates generally to off-road vehicles, such as All-Terrain Vehicles (ATVs) and Utility Vehicles (UTVs), and more specifically to torque-control systems for such vehicles.
Many modern vehicles include systems for controlling traction and stability. These systems often rely on the calculation of estimated wheel torque. For example, engine torque in many automotive applications can be calculated as follows:
Engine Torque=Tractive Forces at Tires/(Transmission Factor*Driveline Efficiency−Inertia Moment Driveline*Rotational Speed Change Rate Driveline]
Because the gear ratio and other inputs are generally known, these inputs are generally fixed and do not vary significantly with changing conditions. As a result, the vehicle's CPU can calculate an estimated wheel torque in order to assist control of traction and stability.
Some vehicles utilize continuously-variable transmissions (CVTs) for transferring power from the engine to the wheels. Some of these vehicles actuate the CVT hydraulically to achieve a desired engine operation under certain conditions. In these situations, the vehicle CPU knows the position of the hydraulic actuator, and thus knows the ratio of the transmission.
ATVs and UTVs commonly include CVTs with variable flyweight centrifugal clutches. In these vehicles, it is difficult to accurately calculate torque because the CPU does not know the gear ratio between the engine and the wheels. Therefore, in these vehicles, it is difficult to perform traction and stability control.
The present invention provides a vehicle (e.g., an ATV/UTV) comprising a body, at least two wheels (e.g., four wheels) supporting the body, a power source (e.g., an engine) providing torque to at least one of the wheels, a torque control system for controlling the torque provided to the wheels. The torque control system has a plurality of slip modes, including a low-slip mode and a high-slip mode. A mode selector (e.g., selectable by a user) is provided for selecting one of the plurality of slip modes, and the torque control system defaults to the low-slip mode on vehicle start up. Preferably, the torque control system further includes a medium-slip mode.
In another aspect, the present invention provides a vehicle having a continuously-variable transmission including a drive member and a driven member, and a torque control system for controlling the torque provided to the wheels. The torque control system is programmed to calculate an estimated primary torque factor and an estimated secondary torque factor. In one embodiment, the drive member comprises a primary pulley, the driven member comprises a secondary pulley, and the continuously-variable transmission further includes a belt coupling the primary pulley and the secondary pulley. Preferably, the torque control system is programmed to calculate the estimated primary and secondary torque factors based on wheel speed and acceleration. The torque control system can also be programmed to calculate a base engine torque based on throttle position and engine speed. In this embodiment, the estimated primary torque factor and estimated secondary torque factor are used to modify the base engine torque calculation.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
Referring to
The illustrated ATV 10 includes a vehicle architecture that is represented in
The CCU 46 is coupled to an engine control unit (ECU) 56 via an appropriate communication system 58, such as CAN or hardwire. The ECU 56 is equipped with EFI controller 60 for precise control of the engine. Information such as engine rpm, throttle position, and torque requested/actual can be communicated between the CCU 46 and ECU 56. Optionally, the input from the mode switch 54 can also be provided 62 to the ECU 56. The ECU 56 controls performance of the engine 64 and throttle body 66, which includes a throttle position sensor (TPS) 68. The engine 64 provides 70 engine torque to the vehicle 40.
One aspect of the invention is to improve the calculated estimation of the torque requested/actual for CVT-equipped vehicles to improve vehicle handling characteristics via the TCS and ABS. In this regard,
The algorithm also calculates a primary torque characterization TP and a secondary torque characterization TS, which are used to modify the engine torque characterization TE. The calculation of primary torque characterization TP involves calculating a primary driveline factor 78 using wheel speed 80 and acceleration 82. The primary driveline factor 78 is derived from physical modeling of primary pulley characteristics through the sub-system or component (attributes may include mass, inertia, speed, geometry, friction coefficient, efficiency, etc.). Vehicle acceleration and wheel speeds are used to improve this model, where remaining attributes are generally fixed or defined by static physical properties. These signals are also used to bias the torque estimate with the influence of actual vehicle interaction and parameters versus engine-based parameters.
The primary driveline factor 78 is then used with TE to arrive at the primary torque characterization TP. Weighting factors are assigned in the calibration process related to accuracy and confidence in Primary Driveline Factor and TE estimates for estimation of TP which represent a complete torque model and estimation related to engine and driveline components upstream and through the primary pulley. The absolute value of TP is converted to a mathematical gain or factor for input to a composite CVT factor which is ultimately used to modify the conventionally-based torque request decision.
The calculation of TS involves calculating a secondary driveline factor 86 using wheel speed 88 and acceleration 90. The secondary driveline factor 86 is derived from physical modeling of driveline-based components including the differential or transaxle. Sub-system or component attributes may include ratio, mass, inertia, speed, geometry, friction coefficient, efficiency, etc. Vehicle acceleration and wheel speeds are used to improve this model, where remaining attributes are generally fixed or defined by static physical properties. These signals are also used to bias the partial-torque estimate with the influence of actual vehicle interaction in particular through the tire-road contact patch at the driven wheels.
The secondary driveline factor 86 is then used to arrive at a secondary torque characterization TS. TS (similar to TP) can be derived from physical modeling of secondary pulley characteristics through sub-system or component (attributes may include mass, inertia, speed, geometry, friction coefficient, efficiency, etc.). The absolute value of TS is converted to a mathematical gain or factor for input to a composite CVT factor which is ultimately used to modify the conventionally based torque request decision.
The primary CVT factor 84, secondary CVT factor 92, and engine torque characterization TE are combined to arrive at a composite CVT factor 94. This can be the addition (or multiplication) of gain factors as per common control system practices. The composite CVT factor 94, engine torque characterization TE, and mode switch input 96 are used to determine an appropriate torque request 98. More specifically, the CCU makes the request to the ECU with an adjustment, if needed, to TE via an offset or multiplication factor (Composite CVT Factor) to enhance the precision of the torque request. This precision increase in turn enhances effectiveness of the user-selectable mode switch function on vehicle-level performance.
As noted above, the mode switch 54 allows the user to select one of multiple driving modes (e.g., multiple ABS modes and/or multiple TCS modes). The primary purpose of the mode switch is to allow the operator of the vehicle to select the levels of brake and traction control system interaction base on driver interaction and terrain conditions. In the illustrated embodiment, there are three different driving modes: Base Mode, Intermediate Mode, and Advanced Mode.
In base mode, brake and traction control system control parameter settings are programmed to recognize and intervene at low or shallow levels of slip generated by braking or accelerating. This is intended to provide high levels of vehicle control assistance. In intermediate mode, brake and traction control system control parameters are adjusted to recognize and intervene at levels of wheel slip which will require and increased level of operator interaction, contribution, and skill which can be intentionally selected by the operator. In advanced mode, brake control parameters are modified to deliver high brake deceleration on most off road surfaces. Traction control function is inhibited such that the operator has full control and range of engine torque via the throttle control. This intentional setting allows for enhanced operator interaction and control of the vehicle.
The mode switch 54 is designed so that the user can easily change the mode of the torque-control system. For example, the mode switch 54 can be a push-button switch that digitally toggles between the three modes with a visual representation of the currently-active mode. In one preferred embodiment, the vehicle is programmed so that the torque-control system defaults to the base mode every time the vehicle is restarted. More specifically, at each ignition on/start cycle, the brake and traction control system will default to the base mode settings regardless of the mode switch position. Mode switch “logic” as recognized by the control system software will require the operator to move the mode switch to base mode prior to selecting intermediate or advanced mode. As such, the mode switch will provide operator command messages or requests. These command messages can be provided either via CAN or by specific continuity or ohm values.
Various features and advantages of the invention are set forth in the following claims.
| Number | Date | Country | |
|---|---|---|---|
| 61536383 | Sep 2011 | US |
