Abstract: A method for reducing oscillations in a vehicle driveline includes transmitting torque to secondary wheels of the vehicle, determining a first rate of change in speed between the secondary wheels and primary wheels, if a second rate of change in speed between secondary wheels and primary wheels is greater than the first rate of change, reducing torque transmitted to the secondary wheels proportional to a ratio of the first rate of change and the second rate of change, and if the second rate of change is less than the first rate of change, using differential and proportional control to change said torque.

Abstract: A system and method for managing a powertrain in a vehicle determines a number of vehicle conditions, and compares them to predetermined conditions to determine whether a secondary axle of the vehicle should be automatically connected to or disconnected from the powertrain. In general, if the speed of the vehicle is above some predetermined speed threshold, the secondary axle is disengaged to increase fuel economy. Conversely, if the speed of the vehicle is below some predetermined threshold, the secondary axle is typically engaged to help maximize the capture of regenerative braking energy during a braking event. Additional vehicle conditions may be examined, and exceptions to the general rule utilized, to further enhance the control strategy.

Abstract: A method for reducing oscillations in a vehicle driveline includes transmitting torque to secondary wheels of the vehicle, determining a first rate of change in speed between the secondary wheels and primary wheels, if a second rate of change in speed between secondary wheels and primary wheels is greater than the first rate of change, reducing torque transmitted to the secondary wheels proportional to a ratio of the first rate of change and the second rate of change, and if the second rate of change is less than the first rate of change, using differential and proportional control to change said torque.

Abstract: A method for controlling operation of a transfer case in a motor vehicle driveline that includes by an engine controlled by a throttle having a variable position, and a transmission driveably connected to the engine for producing multiple ratios of the speed of a transmission input relative to the speed of a transmission output. The transfer case transmitting rotating power in response to an electric signal applied to a clutch. The method includes determining that the engine throttle position is less than a first reference throttle position during a period of predetermined length; determining that a speed of the vehicle speed is in a predetermined range; determining that the transmission is operating in a speed ratio greater than a reference speed ratio; determining that the engine throttle position is greater than a first reference throttle position; and increasing the torque capacity of the clutch for a predetermined period.

Abstract: A method for controlling operation of a transfer case clutch in a motor vehicle driveline controlled by an engine throttle having a variable position. The transfer case transmits rotating power to a primary power path and to a secondary power path in response to an electric current duty cycle applied to a coil that actuates the clutch. The method includes the steps of determining that a current vehicle speed is less than a reference vehicle speed; determining that the engine throttle position is in a reference throttle position range; determining that a change in vehicle speed is greater than a reference change in vehicle speed; using a current magnitude of torque in the driveline to determine a desired duty cycle for the coil; and applying a duty cycle of the desired magnitude to the coil.

Abstract: A method for controlling operation of a transfer case clutch in a motor vehicle driveline controlled by an engine throttle having a variable position. The transfer case transmits rotating power to a primary power path and to a secondary power path in response to an electric current duty cycle applied to a coil that actuates the clutch. The method includes the steps of determining that a current vehicle speed is less than a reference vehicle speed; determining that the engine throttle position is in a reference throttle position range; determining that a change in vehicle speed is greater than a reference change in vehicle speed; using a current magnitude of torque in the driveline to determine a desired duty cycle for the coil; and applying a duty cycle of the desired magnitude to the coil.

Abstract: A method for controlling operation of a transfer case in a motor vehicle driveline that includes by an engine controlled by a throttle having a variable position, and a transmission driveably connected to the engine for producing multiple ratios of the speed of a transmission input relative to the speed of a transmission output. The transfer case transmitting rotating power in response to an electric signal applied to a clutch. The method includes determining that the engine throttle position is less than a first reference throttle position during a period of predetermined length; determining that a speed of the vehicle speed is in a predetermined range; determining that the transmission is operating in a speed ratio greater than a reference speed ratio; determining that the engine throttle position is greater than a first reference throttle position; and increasing the torque capacity of the clutch for a predetermined period.

Abstract: A system and method for managing a powertrain in a vehicle determines a number of vehicle conditions, and compares them to predetermined conditions to determine whether a secondary axle of the vehicle should be automatically connected to or disconnected from the powertrain. In general, if the speed of the vehicle is above some predetermined speed threshold, the secondary axle is disengaged to increase fuel economy. Conversely, if the speed of the vehicle is below some predetermined threshold, the secondary axle is typically engaged to help maximize the capture of regenerative braking energy during a braking event. Additional vehicle conditions may be examined, and exceptions to the general rule utilized, to further enhance the control strategy.

Abstract: In a motor vehicle driveline having an automatic transmission driveably connected to a transfer case whose output is continually connected to a first output, a clutch, selectively engaged in response to a control signal, driveably connects a second output to the first output. A digital computer continually monitors the occurrence of a change of clutch slip, input torque and a torque rate change to control the torque transmitted by the clutch to the second output. The control causes the clutch to transmit torque to the second output having a constant fraction of the input clutch torque and another portion that is proportional to the clutch slip. This result simulates the torque slip characteristics produced by transfer case having both a center differential mechanism and a viscous clutch.

Abstract: A four wheel drive assembly 10 including a torque transfer assembly 60 which operates under the control of the controller 62 and which receives and selectively transfers a certain desired amount of torque to a front axles 14, 15 and to the rear axles 14 17. The amount of transferred torque varies depending upon the occurrence of a sensed slip condition the use of a pre-emptive slip control mode of operation in which the controller 62 determines that it is likely that a slip may occur. Particularly, controller 62 is allowed to enter the preemptive mode of operation only after an actual slip has occurred and the controller 62 exits this preemptive mode of operation upon the occurrence of a certain event or condition or upon the passage of a certain amount of time.

Abstract: In a motor vehicle driveline having an automatic transmission driveably connected to a transfer case whose output is continually connected to a first output, a clutch, selectively engaged in response to a control signal, driveably connects a second output to the first output. A digital computer continually monitors the occurrence of a change of clutch slip, input torque and a torque rate change to control the torque transmitted by the clutch to the second output. The control causes the clutch to transmit torque to the second output having a constant fraction of the input clutch torque and another portion that is proportional to the clutch slip. This result simulates the torque slip characteristics produced by transfer case having both a center differential mechanism and a viscous clutch.

Abstract: A four wheel drive assembly 10 including a torque transfer assembly 60 which operates under the control of the controller 62 and which receives and selectively transfers a certain desired amount of torque to a front axles 14, 15 and to the rear axles 14 17. The amount of transferred torque varies depending upon the occurrence of a sensed slip condition the use of a pre-emptive slip control mode of operation in which the controller 62 determines that it is likely that a slip may occur. Particularly, controller 62 is allowed to enter the preemptive mode of operation only after an actual slip has occurred and the controller 62 exits this preemptive mode of operation upon the occurrence of a certain event or condition or upon the passage of a certain amount of time.

Abstract: A transfer case control system or apparatus 10 is provided for use on a four-wheel drive vehicle of the type having a transfer case 32, a front driveshaft 22 and a rear driveshaft 26. Transfer case control system 10 includes a conventional microcontroller or controller 40 having a memory unit 42 and operating under stored program control. Controller 40 is communicatively coupled to sensors 44, 46, 48, and to transfer case 32. Controller 40 selectively transmits a torque control or “boost torque” signal to transfer case 32, based upon the rate of change of the vehicle's throttle position and the speed of driveshafts 22, 26.

Abstract: A transfer case control system or apparatus 10 is provided for use on a four-wheel drive vehicle of the type having a transfer case 32, a front driveshaft 22 and a rear driveshaft 26. Transfer case control system 10 includes a conventional microcontroller or controller 40 having a memory unit 42 and operating under stored program control. Controller 40 is communicatively coupled to sensors 44, 46, 48, and to a transfer case 32. Controller 40 selectively generates a control signal having a proportional term or component and an integral term or component. The control signal is generated to transfer case 32 and controls the amount of torque provided to driveshafts 22, 26.

Abstract: A transfer case control system or apparatus 10 is provided for use on a four-wheel drive vehicle of the type having a transfer case 32, a front driveshaft 22 and a rear driveshaft 26. Transfer case control system 10 includes a conventional microcontroller or controller 40 having a memory unit 42 and operating under stored program control. Controller 40 is communicatively coupled to sensors 44, 46, 48, and to transfer case 32. Controller 40 selectively transmits a torque control or minimum duty cycle signal to transfer case 32, which is at least partially based upon the angular position of the vehicle's steering wheel and the speed of driveshafts 22, 26.

Abstract: A system 10 for controlling a transfer case clutch assembly is provided and is deployed within a four-wheel drive vehicle having a front driveshaft 22, a rear driveshaft 26, and a transfer case 32 which selectively provides torque to the driveshafts 22, 26 by way of a clutch assembly 38. System 10 includes a controller 40 which is communicatively coupled to the clutch assembly 38. Controller 40 receives signals generated by sensors 44-48, utilizes the received signals to determine the onset of a slip condition, and based upon this determination, generates a command signal to selectively activate the clutch assembly 38 effective to smoothly release torque from the front driveshaft 22 and/or rear driveshaft 26.

Abstract: A transfer case control system or apparatus 10 is provided for use on a four-wheel drive vehicle of the type having a transfer case 32, a front driveshaft 22 and a rear driveshaft 26. Transfer case control system 10 includes a conventional microcontroller or controller 40 having a memory unit 42 and operating under stored program control. Controller 40 is communicatively coupled to sensors 44, 46, 48, and to transfer case 32. Controller 40 selectively transmits a torque control or “boost torque” signal to transfer case 32, based upon the rate of change of the vehicle's throttle position and the speed of driveshafts 22, 26.

Abstract: A transfer case control system or apparatus 10 is provided for use on a four-wheel drive vehicle of the type having a transfer case 32, a front driveshaft 22 and a rear driveshaft 26. Transfer case control system 10 includes a conventional microcontroller or controller 40 having a memory unit 42 and operating under stored program control. Controller 40 selectively generates a control signal which controls the amount of torque provided to driveshafts 22, 26. Controller 40 provides an improved torque adjustment “response” by automatically adjusting to the condition of the vehicle's tires.

Abstract: A four-wheel drive system for a motor vehicle includes a transfer case through which power is continually transmitted to a first drive wheel pair and a clutch that controls a magnitude of torque transmitted to a second drive wheel pair in accordance with an electric current duty cycle applied to the clutch by a control unit that produces an output duty cycle in response to a range selected by the operator, the vehicle speed, and the position of the throttle that controls a power source driveably connected to the input side of the transfer case.

Abstract: A method of monitoring the relative effective diameters of the tires and compensating therefor in a vehicle which includes a front driveshaft for transferring motive power to a front set of wheels and a rear driveshaft for transferring motive power to a rear set of wheels, each of the wheels having an effective diameter. Front and rear driveshaft values indicative of the rotational speed of each driveshaft are generated. A difference value indicative of a difference between said front and rear driveshaft values is then generated. A low pass filtered value is generated according to the relationship of Y.sub.1p =(1-.beta.)*U(k)+.beta.*Y.sub.1p (k-1). The low pass filtered value is monitored for a predetermined period of time to determine if one of the wheels has a smaller effective diameter than the other wheels.