CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This PCT application claims the benefit of priority under 35 U.S.C. §1 19 to United States Patent Application No. 16/362, 155, filed March 22, 2019, the contents of which are incorporated herein by reference in their entirety.

BACKGROUND

1 . Field of the Invention

[0002] The present invention generally relates to systems and methods for controlling the speed of a motor vehicle, especially at low speeds.

2. Description of Related Art

[0003] Autonomous vehicles are vehicles that have the ability to control, in an automated manner their speed and direction steering. However, autonomous vehicles, especially in low speed situations, need to be able to maintain their speed and be able to brake in a sufficient manner.

[0004] Autonomous vehicles that utilize traditional internal combustion r I engines generally utilize a friction type foundation braking system to reduce the speed of the vehicle. However, as is well known, the speed of the vehicle can in part be controlled or reduced by utilizing the engine torque of the vehicle also called engine braking. As such, the engine torque of the vehicle can be utilized to slow down the vehicle instead of or as a compliment to the foundation braking system. Further complicating this, is that when controlling the speed below the crawling speed of the vehicle driven by the minimum engine torque, the brake pedal or brake actuator is the only controllable input to the system. Typical motor vehicles powered by internal combustion engines utilize a powertrain system which applies a certain level of forward motion torque to the road wheels in an idle state, requiring application of the foundation breaks to maintain the vehicle at a standstill.

[0005] As such, controlling a vehicle at low speed environments so that the vehicle operates in a smooth and fluid like manner poses several problems especially with regard of appropriately slowing down the vehicle by either using engine braking, traditional foundation braking, or some combination of the two.

SUMMARY

[0006] A system and method for controlling the speed of a vehicle in accordance with this invention includes a processor, a speed sensor in communication with the processor, a throttle actuator in communication with the processor, and a brake actuator in communication with the processor. The processor is set either to control the throttle position of the vehicle engine via a throttle actuator or the brake actuator position of the vehicle via a brake actuator based upon whether the augmented acceleration is greater than or equal to a gear acceleration, whether the actual speed is above a crawl speed, and a lookup table.

[0007] Further objects, features, and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 illustrates a block diagram of a vehicle having a system for controlling the steering of the vehicle;

[0009] Figure 2 illustrates a block diagram of a steering control system;

[0010] Figure 3 illustrates a block diagram of a throttle control system and a brake control system;

[0011] Figure 4 illustrates a method for controlling the speed of the vehicle; and [0012] Figures 5A, 5B and 6 illustrate look up tables.

DETAILED DESCRIPTION

[0013] Referring to Figure 1 , a motor vehicle 100 is shown. It should be understood that the vehicle 100 could be any type of vehicle capable of transporting persons or items from one point to another. As such, the vehicle may be a car, truck, commercial vehicle, tractor trailer, farm tractor, mining vehicle, and the like.

[0014] It should be noted that in this specification and the claims both velocity and speed are referenced. Applicant acknowledges that velocity is a vector variable designating both magnitude and direction whereas speed is a scaler. For purposes of this invention these terms can be used interchangeably as velocity is only considered with regard to its magnitude (positive or negative).

[0015] Here, the vehicle 100 includes a processor 102. The processor 102 may be a single processor of may be multiple processors working in concert. Generally, the processor is arranged within the interior of the vehicle 100. The processor 102 may be separately connected to or may incorporate a memory device 103. Here, the memory device 103 is shown to be integrated within the processor 102, but it should be understood that the memory device 103 may be separate from the processor 102. The memory device 103 may be any type of memory device capable of storing digital information. As such, the memory device 103 may be a solid-state memory device, optical memory device, magnetic memory device, and the like. The memory device may include instructions 105 and/or other data, such as lookup tables. In the case of instructions, instructions may include executable code for executing any one of the methods disclosed in this specification.

[0016] The processor 102 may be connected to a number of different sensors for sensing different physical parameters of the vehicle. For example, the processor 102 may be in communication with the velocity sensor 104. The velocity sensor 104 may be a wheel speed sensor mounted and arranged within the vehicle 100 so as to be able to determine the wheel speed of at least one wheel 106 of the vehicle. Of course, it should be understood that the vehicle 100 may have multiple wheel speed sensors for each of the road engaging wheels.

[0017] Additionally, the vehicle 100 may include an accelerometer 108 also in communication with the processor 102. The accelerometer 108 is capable of determining the acceleration of the vehicle 100 and is mounted in the vehicle to accomplish this task. The accelerometer 108 may measure acceleration any one of a number of directions including lateral and/or transverse acceleration. The vehicle 100 may also include a steering wheel angle sensor 1 10 configured to determine the steering wheel angle of the vehicle 100.

[0018] The processor 102 may be connected to a number of different vehicle systems capable of controlling the vehicle 100. For example, the processor 102 may be in communication with a steering control system 1 12. The steering control system 1 12 may be connected to a steering system that essentially controls the steering of the vehicle 100 based on instructions from the processor 102.

[0019] The processor 102 may also be in communication with a throttle control system 1 14. The throttle control system 1 14 is configured to control the throttle position of the engine of the vehicle. As the throttle position of the engine of the vehicle changes, the vehicle can be controlled to change speeds.

[0020] The processor 102 may also be in communication with the brake control system 1 16 as configured to control the brakes of the vehicle. The brakes of the vehicle allow the vehicle to slow down and/or remain in a stopped position. The brake control system 1 16 receives instructions from the processor 102 and is able to actuate the vehicle brakes so as to slow the vehicle 100 down or maintain it in a stopped position. It should be understood that the throttle control system 1 14 in the brake control system 1 16 may be incorporated within a single control unit. This may be because the ability to control the brakes and/or throttle the vehicle are both related to controlling the speed of the vehicle.

[0021] The processor 102 may also be in communication with an autonomous vehicle control system 120 that provides instructions to the processor to relay these instructions to any which one of the vehicle control systems, such as the steering control system 1 12, throttle control system 1 14 and/or the braking control system 1 16. For example, the autonomous vehicle control system 120 may provide instructions to the processor 102 to accelerate the vehicle, slow down the vehicle, apply the brakes, and other commands. These commands may be arrange as an array of commands.

[0022] Referring to Figure 2, a more detailed diagram of the steering control system 1 12 is shown. Here, the steering control system receives a target yaw rate 202 for the vehicle to be steered towards. An inverse yaw gain module 204 determines a target road wheel angle 206. The steering ratio module 208 takes the target road wheel angle 206 and creates a target hand wheel angle 210. From there, a steering angle controller 212 takes the target hand wheel angle 210 and determines an amount of torque 214 to apply to a steering system 216.

[0023] From there, as the steering system 216 steers the vehicle, the hand wheel angle changes and is fed back into the steering angle controller 212. An automated controller 220 may also be utilized to automate the vehicle yaw rate determination.

[0024] Referring to Figure 3, a more detailed view of the throttle control system 1 14 and brake control system 1 16 is shown. It could be understood that the throttle control system 1 14 and the brake control system 1 16 may be separate components or may be integrated together as shown in Figure 3.

[0025] Here, a filtering and estimation module 304 receives a target speed 302. The filtering estimation module 304 determines a target speed 302 and a target acceleration 306 from the target speed 302. In addition, a filtering estimation module 304 determines the actual speed 308 that may be provided by the velocity sensor 104, which as stated previously, may be a wheel speed sensor.

[0026] Also shown is a switch 310. The switch 310 determines if the throttle or brake should be controlled. This switch 310 may have the ability to control both the throttle and the brake at the same time. Here, the throttle controller 312 communicates to the throttle body 314 which then adjusts the throttle position 316 of the vehicle 100. By adjusting the throttle position, the vehicle can be slowed down or sped up.

[0027] Referring to Figure 4, a method for controlling the vehicle is shown. Here, in step 402, the processor 102 is configured to measure an actual velocity of the

vehicle. This may be accomplished by receiving information from the velocity sensor 104. In step 404, the processor 102 receives a target velocity and the actual velocity

°f the vehicle. The target velocity may come from the autonomous

vehicle control system 120 and the actual velocity may come from the velocity sensor 104.

[0028] In step 406, the processor is configured to receive the target acceleration which may come from the autonomous vehicle control system 120.

[0029] In step 408, the processor 102 is configured to determine augmented acceleration based on the target velocity and actual velocity

Alternatively, the augmented acceleration may be based on the target velocity

actual velocity and a grade (q) of a road the vehicle is travelling on. In

one example:

wherein l is a tunable parameter, providing closed loop feedback for variation and disturbance rejection and wherein p is a tunable parameter providing compensation for road grade. [0030] Thereafter, in step 410, a determination is made whether the actual velocity ' ^s above the crawl speed of the vehicle. This crawl speed of the vehicle is generally defined as the speed in which the vehicle maintains when it is at idle, on a level road surface and in gear and may be about 6 kph. If the actual velocity is above

the crawl speed, the method continues to step 412.

[0031] In step 412, a determination is made if the augmented acceleration is less than the gear acceleration. If this is the case, the processor 102 is configured, as shown in step 414, to set the throttle position of the vehicle by the throttle control system 1 14 based on the look-up table to decelerate the vehicle. If not, the method to step 416 wherein the processor is configured to set the brake actuator position using the braking control system 1 16 based on the look-up table to decelerate the vehicle.

[0032] If we step back to step 412; if it is determined that the actual velocity is not above a crawl speed, the method continues to step 418 wherein the processor 102 is configured to set the brake actuator position of the vehicle by the brake control system 1 16 based on the look-up table to decelerate the vehicle.

[0033] After steps 414, 416, or 418 of an executed, the method then returns again to step 402.

[0034] Referring to Figures 5A and 5B, a graph of a look-up table for determining to control the speed of the vehicle using either the throttle control system 1 14 or the brake control system 1 16 is shown. Figure 5a illustrates a line 502 that demarks when a throttle control should be utilized or when a brake control is utilized. The throttle control is utilized when located above the line 502 and the brake control is utilized when located below the line 502. The inventors have noticed that using a look-up table disclosed in Figure 5a may result in poor control of the vehicle especially at low speeds. As such, as shown in Figure 5b, a modified look-up table wherein the line 504 is utilized to demark between when utilizing the throttle control and the brake control. As can be seen in Figure 5b, brake control is utilized in increasing fashion as the speed of the vehicle decreases. By so doing, the vehicle 100 will be under better control at lower speeds.

[0035] Figure 6 illustrates a brake actuator look-up table 602 utilized to determine the brake actuator position 604. As input to the look-up table 602 an augmented acceleration is determined so as provided input to the brake actuator look-up table 602. Based on the brake look-up table 602, an actuator position will be outputted 604 and this actuator position is then outputted to the brake control system.

[0036] If the brake system is utilized, a brake look-up table 318 is utilized so as to determine how much force of the brake should be utilized based on the target speed 302, the target acceleration 306 and the actual speed 308. This look-up table provides the appropriate amount of brake actuator pressure to the data speed brake box 320 which in turn adjusts the brake actuator position 322 of the vehicle 100. The brake lookup table 318 may be stored within the memory device 103 of Figure 1. As such, the brake of the vehicle can be applied and removed and a certain amount of pressure can be applied to the brake actuator. This eventually results in a vehicle speed 324 which is then fed back into the filtering and estimation module 304.

[0037] In accordance with various embodiments of the present disclosure, the methods described herein may be implemented by software programs executable by a computer system. Further, in an exemplary, non-limited embodiment, implementations can include distributed processing, component/object distributed processing, and parallel processing. Alternatively, virtual computer system processing can be constructed to implement one or more of the methods or functionality as described herein.

[0038] Further the methods described herein may be embodied in a computer- readable medium. The term "computer-readable medium" includes a single medium or multiple media, such as a centralized or distributed database, and/or associated caches and servers that store one or more sets of instructions. The term "computer-readable medium" shall also include any medium that is capable of storing, encoding or carrying a set of instructions for execution by a processor or that cause a computer system to perform any one or more of the methods or operations disclosed herein.

[0039] As a person skilled in the art will readily appreciate, the above description is meant as an illustration of the principles of this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modification, variation, and change, without departing from the spirit of this invention, as defined in the following claims.