BATTERY PROTECTION WITH DOWNHILL CHARGE SUSTAIN

Downhill charge sustain battery protection strategy is disclosed. For one example, a vehicle is powered by an electric motor and battery. The vehicle includes a vehicle control unit (VCU) to control friction braking and regenerative braking for the vehicle. For one example, the VCU is configured to implement a method comprising detecting a condition to switch back and forth between regenerative braking and friction braking. For one example, the detected condition is a charge sustain event such as, for example, the vehicle being at a top of a hill or going down a hill in a lift condition (no pedals pressed) and the battery is fully charged at maximum state of charge (SOC) or voltage limit.

FIELD

Embodiments of the invention are in the field of electric power and control systems for vehicles using electric motors. More particularly, embodiments of the invention relate to battery protection with downhill charge sustain.

BACKGROUND

Electric powered vehicles are gaining popularity due to its use of clean energy. Such vehicles have electric motors which can be powered by rechargeable batteries. Electric motors are continuously connected to a battery and the wheels of a vehicle. In one instance, an electric motor can receive power from the battery and generate torque to rotate the wheels of the vehicle which cause the vehicle to move. In another instance, the electric motor can be inverted to receive kinetic energy from the motion of the wheels and generate electric power used to recharge the battery. This process of inverting the electric motor can slow the vehicle and is referred to as regenerative braking. Regenerative braking is an energy recovery process that slows the vehicle down by converting kinetic energy into electrical energy unlike friction braking which uses brake pads to slow a vehicle.

In certain instances, a battery can be fully charged while a vehicle is experiencing a sudden acceleration event such as coasting down a hill, which can cause a runaway condition in terms of vehicle speed. If a brake pedal is pressed and manual or friction braking is applied, the brakes may overheat in this runaway condition. And, if the accelerator pedal is in a lift position as well as the brake pedal, the motor is still continuously connected to the wheels and the rotation of the wheels provides kinetic energy to the motor recharging the battery. In the event of the battery charging during a runaway condition, this can be problematic because the battery may overcharge beyond its maximum limit causing the voltage level in the individual cells of the battery to surge. As a result, the thermal level in the battery can spike, possibly causing the battery to catch on fire. Such an event can be dangerous to the driver and passengers and may cause severe damage to the vehicle.

SUMMARY

Embodiments and examples are disclosed to implement a downhill charge sustain battery protection strategy. For one example, a vehicle is powered by an electric motor and battery. The vehicle includes a vehicle control unit (VCU) to control friction braking and regenerative braking for the vehicle. For one example, the VCU is configured to implement a method comprising detecting a condition to switch back and forth between regenerative braking and friction braking. For one example, the detected condition is a charge sustain event such as, for example, the vehicle being at a top of a hill or going down a hill in a lift condition (no pedals pressed) and the battery is fully charged at maximum state of charge (SOC) or voltage limit.

Because the electric motor is continuously connected to the wheels and battery, even if no pedals are pressed, the rotation of the wheels going down-hill creates kinetic energy which is converted to electrical energy by the electric motor and supplied to the battery. In this process of regenerative braking, the electric motor is not generating torque to drive the wheels, but rather generating electric energy used for recharging the battery. However, if the battery is fully charged when going down-hill, regenerative braking may overcharge the battery beyond its SOC or voltage limit. Thus, in this charge sustain event, switching back and forth between regenerative braking and friction braking can protect the battery from overcharging beyond its maximum limit. The VCU can trigger the switching between regenerative braking and friction braking at a frequency range of greater than 100 hertz and less than 400 hertz. Such a frequency range can avoid vibration and prevent unwanted noise within the vehicle.

For one example, friction braking may cause the temperature on brake components to rise at or beyond an acceptable limit or threshold which can be detected by the VCU. In such an instance, the VCU can blend-out friction braking and blend-in regenerative braking decreasing the temperature on the brake components. For one example, the VCU can also detect if the battery reaches an acceptable SOC or voltage limit or threshold to blend-out regenerative braking and blend-in friction braking to sustain a sufficient charge on the battery. In this way, the charge sustain event battery protection strategy can also prevent overheating of brake components.

Other systems, apparatuses, computer readable-mediums and vehicles are described.

DETAILED DESCRIPTION

The following detailed description provides embodiments and examples to implement a downhill charge sustain battery protection strategy. For one example, a vehicle includes a vehicle control unit (VCU). The VCU detects a charge sustain event condition to trigger a braking strategy of switching between regenerative braking and friction braking that can sustain a sufficient charge for the battery without exceeding its maximum limits and even prevent braking components from overheating.

One example condition to trigger a charge sustain event is a vehicle at or near a top of a hill or going down a hill in a lift condition (no pedals pressed) and the battery is fully charged at its maximum state of charge (SOC) or voltage limit. In this condition, the vehicle may experience a break-away speed situation and instead of continuously applying regenerative braking, which can charge the battery beyond is maximum SOC and voltage limit, the VCU can switch the vehicle between regenerative braking and friction such that the battery does not exceed its maximum SOC and voltage limit. If a temperature of one of the braking components exceeds a maximum limit, the VCU can also blend-out friction braking and blend-in regenerative braking thereby preventing braking components from overheating.

For one example, the VCU is coupled to a location data source to calculate a location of the vehicle and one or more sensors to receive sensor data including temperature, SOC, voltage, etc. related to one or more components of the vehicle. Other charge sustain event conditions to trigger switching between regenerative braking and friction braking can include a temperature of one or more braking components at or beyond a threshold or limit, a temperature related to the battery at or beyond a threshold or limit, or a SOC or voltage level of the battery at or beyond a threshold or limit or any combination of these conditions.

As set forth herein, various embodiments, examples and aspects will be described with reference to details discussed below, and the accompanying drawings will illustrate various embodiments and examples. The following description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of various embodiments and examples. However, in certain instances, well-known or conventional details are not described to facilitate a concise discussion of the embodiments and examples. Although the following examples and embodiments are directed to a battery protection strategy for vehicles, the battery protection strategy disclosed herein can be implemented for any type machine, apparatus, or device using an electric motor and battery.

Exemplary Vehicle with Battery Protection Strategy

FIG. 1illustrates one example of a vehicle100capable of implementing a charge sustain event battery protection strategy. Vehicle100includes an electric motor108coupled to battery103and wheels109, brake system110, and a powertrain system120having a vehicle control unit107. For one example, vehicle100can be a hybrid, autonomous or non-autonomous vehicle or electric car. Although vehicle100is shown with one electric motor108for a two-wheel drive implementation, vehicle100can have a second electric motor for a four-wheel drive implementation. For one example, brake system110and powertrain system120include one or more electronic control units (ECUs) such as VCU107. For one example, ECUs can be a micro-controller, computing or data processing system, system-on-chip (SOS), or any embedded system that can run firmware or program code stored in one or more memory devices to perform operations or functions and control various components within vehicle110. For example, brake system110can control friction braking to wheels10and powertrain system120can have electric motor108provide torque to drive wheels109and invert electric motor108to provide regenerative braking and recharge battery103. The ECUs can be coupled by way of a network topology within vehicle100and communicate signals, requests, commands, and etc.

Battery103is a rechargeable battery and can power electric motor108or other electric motors for vehicle100. Examples of battery103can include lead-acid, nickel-cadmium, nickel-metal hydride, lithium ion, lithium polymer, or other types of rechargeable batteries. For one example, battery103can be located on the floor and run along the bottom of vehicle100. As a rechargeable battery, for one example, battery103can be charged by being plugged into an electrical outlet. And, for another example, battery103can be charged during regenerative braking when electric motor108is inverted (not supplying torque to drive wheels109) and converting kinetic energy from rotating wheels109into electrical energy used for recharging battery103. The location and number of batteries is not limited to one and can be located throughout vehicle100in any location.

Examples of electric motor108can include alternating current (AC) induction motors, brushless direct-current (DC) motors, and brushed DC motors. Exemplary motors can include a rotor having magnets that can rotate around an electrical wire or a rotor having electrical wires that can rotate around magnets. Other exemplary motors can include a center section holding magnets for a rotor and an outer section having coils. For one example, when driving wheels109, electric motor108contacts with battery103providing an electric current on the wire that creates a magnetic field to move the magnets in the rotor that generates torque to drive wheels109. When inverted, the contacts between the electric motor108and battery103allow electric motor108to generate electric energy from kinetic energy derived from rotating wheels109. For instance, the magnetic field from rotating magnets in rotor can create electrical current in the wire to generate electrical energy supplied to battery103. This conversion of kinetic energy to electrical energy can be used to slow the speed of vehicle100during regenerative braking and the generated electrical energy can recharge battery103.

In this example, electric motor108is located at the rear of vehicle100to drive back wheels110as a two-wheel drive vehicle. For other examples, another electric motor can be placed at the front of vehicle100to drive front wheels109as a four-wheel drive vehicle. In motion, electric motor108is continuously connected to battery103and wheels109and is either driving wheels109or recharging battery103. For example, in one direction, electric motor108can receive electrical energy from battery103to create a torque to drive wheels108. In the other direction, electric motor108can receive kinetic energy from rotating wheels108and generate electrical energy and supplied to battery103as part of regenerative braking.

For one example, brake system110provides braking functions for wheels109including friction braking using brake pads. Powertrain system120controls electric motor108to drive wheels109or inverts electric motor108for regenerative braking to slow the speed of vehicle100when electric motor is not driving wheels109. For one example, brake system110and powertrain system120communicate signals providing limits and parameters for friction braking and regenerative braking. For example, torque limits for friction braking and regenerative braking can be exchanged between brake system110and powertrain system120.

For one example, VCU107of the powertrain system120can detect a charge sustain event condition and trigger brake system110and powertrain system120to implement a battery protection strategy of switching between regenerative braking and friction braking. For example, VCU107can receive location data for vehicle100to determine that vehicle100is at or near a top of a hill or going down a hill. VCU107can also receive sensor data or signals from vehicle components indicating that the vehicle100is in a lift condition (no pedals pressed) and battery103is fully charged at its maximum state of charge (SOC) or voltage limit. In this condition, VCU107can determine vehicle100is in a charge sustain event because vehicle100may enter a break-away speed situation that continuously recharges battery103during regenerative braking because electric motor108is not driving wheels109. Alternatively, if this condition is detected, VCU107can trigger a battery protection strategy of switching between regenerative braking and friction braking. VCU107can control switching of regenerative braking and friction braking such that the charge on battery103does not exceed its maximum SOC and voltage limit while sustaining a sufficient charge for the battery103.

For other examples, VCU107can detect other types of charge sustain events including detecting a temperature of one or more braking components at or beyond a threshold or limit, a temperature related to battery103at or beyond a threshold or limit, or a SOC or voltage level of the battery103at or beyond a threshold or limit or any combination of these conditions. Thus, such a battery protection strategy can also prevent braking components from overheating. Although VCU107is shown as part of powertrain system120, VCU107can be a separate controller within vehicle100and part of other systems to communicate with any number of ECUs controlling other operations and functions for vehicle100.

Exemplary Battery Protection Strategy Systems

FIG. 2Aillustrates one example of a block diagram of a system200for vehicle100to implement a charge sustain battery protection strategy. Referring toFIG. 2A, system200includes a brake system210coupled to a powertrain system220. Brake system210includes a brake controller unit (BCU)212, electro-mechanical brake booster (brake booster)213, electronic stability programs (ESP)/anti-lock braking systems (ABS)214and brakes215having brake pads. BCU212can control the brake booster213, ESP/ABS214to control the brake pads of brakes215in providing friction braking. The brake booster213can be used to boost a brake pedal pressure for friction braking and can boost the electrical signal for braking purposes. In other examples, for a brake-by-wire system brake booster213can be omitted and braking caused by pressing of a brake pedal can be performed electronically.

Powertrain system220includes a vehicle control unit (VCU)207, inverter226, and electric motor208. VCU207can control inverter226and electric motor208to drive wheels109and generate electrical power to recharge battery103. VCU207and BCU212can also communicate with each to trigger a sustain charge event and modulate friction braking by BCU212in the brake system210and regenerative braking by VCU207in powertrain system220as detailed inFIG. 2B. BCU212and VCU207can include any type of micro-controller, electronic control unit (ECU), system on a chip (SOC), central processing unit (CPU), microprocessor, data processing system or computing system or other components (e.g., memory devices) as described inFIG. 7.

For one example, VCU207is coupled to sensors203and location information source202. Location data source202can be an in-vehicle mapping application having mapping data to identify a location for vehicle100and include a GPS device to receive precise GPS location data to calculate a geographical position for vehicle by location data source202and forwarded to VCU207. For one example, VCU207can receive location information from location data source202to detect that that vehicle100is at or near the top of a hill. For one example, sensors203include any number and types of sensors providing sensor data. For example, sensors203can includes sensors to provide brake component temperature, battery103temperature, state of charge (SOC) and voltage levels for battery103, and other types of sensor data to VCU207. The information and data provided by location information source202and sensors203to VCU207can be used to detect a sustain charge event condition such as, for example, vehicle100is at the top of a hill to experience a down-hill scenario and battery103is fully charged at its maximum SOC. Other examples of charge sustain event conditions detected by VCU207to trigger switching between regenerative braking and friction braking can include a temperature of one or more braking components in brake system210at or beyond a threshold or limit, a temperature related to battery103at or beyond a threshold or limit, or a SOC or voltage level of battery103at or beyond a threshold or limit or any combination of these conditions.

For one example, if a charge sustain event condition is detected, VCU207can signal BCU212to trigger modulation of friction braking to brakes215and VCU207can also trigger modulation of regenerative braking by electric motor208such that regenerative braking alternates with friction braking. For one example, modulation of friction braking and regenerative braking can be offsetting having sinusoidal signals where regenerative braking can blend-out while friction braking blends-in and vice versa. For one example, the modulated signals can alternate at a frequency range of greater than 100 hertz (Hz) and less than 400 Hz. Such a frequency range can prevent noticeable vibration to a driver or passenger of vehicle100or disruptive noise caused by switching between regenerative braking and friction braking.

FIG. 2Billustrates exemplary communication between brake system210and powertrain system220to implement a charge sustain event battery protection strategy. Referring toFIG. 2B, only the BCU212for brake system210and VCU207for powertrain system220are shown. For one example, VCU207and BCU212can communicate signals291through297for a charge sustain event condition to implement a battery protection strategy.

Initially, for signal291, BCU212sends to VCU207torque limits for powertrain system220under normal driving operation. For example, referring toFIG. 1, a rear-axle two-wheel drive implementation, BCU212can send the minimum and maximum rear axle torque limits for electric motor108to drive wheels109. In other examples, BCU212can send front axle torque limits for another electric motor108to drive wheels109. Such limits can refer to stability limits for vehicle100.

For signal292, VCU207can detect charge sustain event condition and enable powertrain system220to switch between regenerative braking and friction braking. The VCU207indicates to BCU212of the charge sustain event and enabling of alternating between regenerative braking and friction braking by modulating brake control signal231and motor control signal233received by electric motor208and friction brakes215for wheels209as shown inFIG. 2C.

For signal293, the BCU212sends friction brake torque limits to VCU207indicating braking capabilities for brake system210for braking of wheels109of vehicle100. For one example, BCU212informs VCU207of powertrain system220of what brake system210is capable of providing for friction braking, e.g., newton-meters of torque at each wheel109. VCU207uses this friction brake torque limits to limit or control the charge-sustain braking or modulation of regenerative braking to achieve a desired charge sustain on battery103based on friction brake limit signal293from BCU212.

For signal294, VCU207informs BCU212of the amount of friction brake torque target and modulation speed for friction braking to be applied by brake system210. For example, VCU207informs BCU212of the rate at which switching or blending of friction braking and regenerative braking should occur during the charge sustain event condition. For one example, VCU207informs BCU212to switch or alternate friction braking at a modulation speed or frequency in the range of around 100 hertz (Hz) and less than 400 Hz.

For signal295, BCU212sends an estimated brake torque signal295to VCU207of the brake torque applied by brake system210for friction braking during the charge sustain event. That is, the estimated brake torque signal informs VCU207of the actual torque applied by brake system210during modulation of the friction braking.

For signal296, brake system210may receive a brake pedal request. For this example, BCU212sends the brake pedal request296to VCU207. ForFIG. 2B, vehicle100can operate in a brake-by-wire implementation or in a manual or non-brake by wire implementation as described inFIG. 2D. For one example, in a non-brake by wire implementation, VCU207can disable the charge sustain event braking and brake system210can process the brake pedal for standard friction braking using brake booster213and ESP/ABS214and brake pads of brakes215. For another example in this driver braking scenario, in a brake-by-wire implementation, VCU207would send a modification of signal294to indicate a portion to add in the braking applied by the brake pedal as shown in friction braking level273inFIG. 2D. This can apply the brake pedal request in order to minimize latency. In other examples of a brake-by-wire implementation, the brake pedal request can be adjusted and the sustain charge braking operation can continue.

For signal297, VCU207informs BCU212to process brake pedal and that a lift-pedal torque was applied as shown by regenerative braking torque272shown inFIG. 2D. This can be a verification that powertrain system220is operating within vehicle limits and charge sustain event can be discontinued.

FIG. 2Dillustrates exemplary graphs showing comparison of regenerative braking blending-in for non-brake-by-wire and brake-by-wire implementations with respect to pressing of an accelerator pedal and brake pedal. Referring toFIG. 2D, for the non-brake by wire example, as the percentage of the accelerator pedal pressure261decreases (going in a lift position or lift pedal position), regenerative braking torque262blends-in and reaches full regenerative braking as the accelerator pedal is in a full lift position. For one example, as a brake pedal is being fully pressed and accelerator pedal is in lift pedal position, friction braking level263rises and regenerative braking torque262can blend-out.

For the brake-by-wire example, as the percentage of the accelerator pedal pressure271decreases to go in a lift position, regenerative braking torque272rises to a first level. And, if a brake pedal is pressed and in lift pedal position, regenerative braking torque272rises to a second level while friction braking level273rises to a first level of friction braking as it is blended-in and then friction braking can go to a full level and as regenerative braking torque272is blended-out. In the break-by-wire implementation, braking can be controlled electronically to receive the full benefit of regenerative braking and friction braking.

Exemplary Battery Protection Operations

Referring to operation300ofFIG. 3A, at operation302, a charge sustain event is detected. For example, a charge sustain event can be a vehicle at or near a top of a hill or going down a hill in a lift condition (no pedals pressed) at break-away speed and the battery is fully charged at its maximum state of charge (SOC) or voltage limit. At operation304, for the detected charge sustain event, vehicle100using brake system210and powertrain system220alternates between friction braking and regenerative braking to sustain a charge for battery103while preventing battery103from overcharging.

Referring to operation350ofFIG. 3B, at operation352, friction braking can be applied until braking temperature reaches a limit. For example, friction brakes212can include a temperature sensor to measure a temperature of the friction brakes which can comprise of a rotor and contact pads. The measured temperature can be received by VCU207. Once the measured temperature reaches a limit, at operation352, VCU207can signal to BCU212to modify or blend-out friction braking in order to reduce braking temperature. In this way, charge-sustain braking can also prevent braking components from overheating.

FIG. 4illustrates exemplary graphs408and410of switching or alternating between friction braking and regenerative braking for vehicle100with relation to braking temperature406, battery state of charge (SOC)404, and parasitic elements402in a downhill condition or fast acceleration state for vehicle100. Referring toFIG. 4, graph408shows regenerative braking turning on or off that is offset with graph410showing friction braking turning on and off. As shown, as regenerative braking turns off, friction braking turns on and vice versa.

As shown in graphs404and406, as the state of charge (SOC) of battery103rises when regenerative braking is on and the electric motor203operates as a power generator to charge battery103. As the SOC rises to near or at full charge, regenerative braking is turned off and friction braking is turned on. When friction braking is turned on, braking temperature rises as shown in graph406. When braking temperature reaches a certain level or limit, friction braking is turned off and regenerative braking is turned on to cool down the friction brakes. This alternating process continues until vehicle100has reached a stable condition, e.g., at the bottom of a hill407or the vehicle has stopped. Graph402illustrates that parasitic elements (e.g., fans, heaters, etc.) may affect SOC and brake temperature during the downhill or fast acceleration braking operation.

FIG. 5illustrates another exemplary flow diagram of a battery protection operation500for the vehicle100ofFIGS. 1-2D. Referring toFIG. 5, at operation502, battery103is detected if it is at full charge or state of charge (SOC) is at its limit. At operation504, a downhill scenario is detected. For one example, VCU204can receive location information from location information source202to determine if vehicle100is at or near the top of a hill or going down a hill at break-away speed. If battery103is fully charged and vehicle100is in a downhill scenario and regenerative braking is occurring, at operation506, friction braking is triggered to blend-out regenerative braking at operation508. At operation510, a calibrated minimum is detected. For example, referring to graph404ofFIG. 4, when the SOC hits a minimum, a calibrated minimum is reached. At operation512, if a calibrated minimum is reached, regenerative braking is blended-in and friction braking is blended-out at operation514.

FIG. 6A-6Dillustrates exemplary graphs of switching or alternating between friction braking and regenerative braking with relation to vehicle velocity and battery state of charge (SOC) during a downhill situation. Referring toFIG. 6A, during a downhill situation, the velocity for vehicle100can be at 50 km/h for a period of 2.5 milliseconds (ms). Referring toFIG. 6B, for one example, the SOC reaches 100% during regenerative braking mode and decreases to 97% during friction braking mode. Referring toFIGS. 6C and 6D, signals to trigger friction braking and regenerative braking are alternating or offsetting to cause the SOC to rise to at or near 100% and to sustain a charge of 97% for battery103. Table 1 below illustrate exemplary data values for time, velocity, battery state of charge, friction brake requests, regenerative torque requests and total requests during a protective operation.

Exemplary Data Processing or Computing System

FIG. 7illustrates one example of a data processing system or computing system700, which can be used for any of the systems or electronic control units (ECU) as shown inFIG. 1-6. AlthoughFIG. 7illustrates various components of a data processing or computing system, the components are not intended to represent any particular architecture or manner of interconnecting the components, as such details are not germane to the disclosed examples or embodiments. Network computers and other data processing systems or other consumer electronic devices, which have fewer components or perhaps more components, may also be used with the disclosed examples and embodiments.

Referring toFIG. 7, computing system700, which is a form of a data processing or computing system, includes a bus701, which is coupled to processor(s)702coupled to cache704, display controller714coupled to a display715, network interface717, non-volatile storage706, memory controller coupled to memory710, I/O controller718coupled to I/O devices720, and database712. Processor(s)702can include one or more central processing units (CPUs), graphical processing units (GPUs), a specialized processor or any combination thereof. Processor(s)702can retrieve instructions from any of the memories including non-volatile storage706, memory710, or database712, and execute the instructions to perform operations described in the disclosed examples and embodiments.

Examples of I/O devices720include mice, keyboards, printers and other like devices controlled by I/O controller718. Network interface717can include modems, wired and wireless transceivers and communicate using any type of networking protocol including wired or wireless WAN and LAN protocols including LTE and Bluetooth® standards. Memory710can be any type of memory including random access memory (RAM), dynamic random-access memory (DRAM), which requires power continually in order to refresh or maintain the data in the memory. Non-volatile storage706can be a mass storage device including a magnetic hard drive or a magnetic optical drive or an optical drive or a digital video disc (DVD) RAM or a flash memory or other types of memory systems, which maintain data (e.g. large amounts of data) even after power is removed from the system.

For one example, memory devices710or database712can store GPS or location information for vehicle100. For other examples, memory devices710or database712can store user information of vehicle100. Although memory devices710and database712are shown coupled to system bus701, processor(s)702can be coupled to any number of external memory devices or databases locally or remotely by way of network interface717, e.g., database712can be secured storage in a cloud environment. For one example, processor(s)702can implement techniques and operations described inFIGS. 1-6D.

Examples and embodiments disclosed herein can be embodied in a data processing system architecture, data processing system or computing system, or a computer-readable medium or computer program product. Aspects, features, and details of the disclosed examples and embodiments can take the hardware or software or a combination of both, which can be referred to as a system or engine. The disclosed examples and embodiments can also be embodied in the form of a computer program product including one or more computer readable mediums having computer readable code which can be executed by one or more processors (e.g., processor(s)702) to implement the techniques and operations disclosed inFIGS. 1-6D.