Controlling user-selectable vehicle deceleration rates to maximize regenerative propulsion system

Abstract

An electric regenerative and vehicle deceleration control method includes operating an electrified powertrain in a normal or maximum regenerative mode associated with smaller and larger electric regenerative and vehicle deceleration rates, respectively, receiving an input from a driver of the vehicle indicative of a request to enable the maximum regenerative mode, detecting a status indicative of availability of the maximum regenerative mode, and in response to receiving the request and based on the status of the maximum regenerative mode and a current vehicle deceleration rate: (i) operating the electrified powertrain in the maximum regenerative mode or the normal regenerative mode, (ii) selectively outputting a message to the driver indicative of the status of the maximum regenerative mode, and (iii) selectively commanding a hydraulic brake system of the vehicle to generate a brake force based on a vehicle deceleration rate expected by the driver associated with the regenerative mode in operation.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Patent Application No. 16 / 776,906, filed January 30, 2020, the contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates generally to electrified vehicles and, more particularly, to controlling a user-selectable vehicle deceleration rate to maximize regeneration of an electrified propulsion system. Background Art

[0004] An electrified vehicle includes a battery system that supplies electrical current to power at least one electric motor. The electric motor can be utilized to propel or start the internal combustion engine of the electrified vehicle. Electrified vehicles typically include an electrical regeneration system (e.g., a regenerative braking system) that converts the vehicle's kinetic energy into electrical energy for recharging the battery system and / or for powering vehicle accessory loads. Conventional electrified vehicles have a single regeneration mode, which may not be optimal (i.e., the battery system may be able to receive a greater amount of electrical energy for recharging). In addition, the regeneration mode increases the deceleration rate or "coastdown" rate of the electrified vehicle. Because the regeneration mode is almost always enabled, the driver expects the associated vehicle deceleration rate. However, when the regeneration mode is not available, the vehicle may experience a different deceleration rate, which may be undesirable for the driver. Therefore, while such electrified vehicle systems work well for their intended purposes, there is an opportunity to improve the related technology. Summary of the Invention

[0005] According to an exemplary aspect of the present invention, an electric regeneration and vehicle deceleration control system for an electrified vehicle is provided. The electrified vehicle has an electrified powertrain including an engine and at least one electric machine. In one exemplary embodiment, the control system includes a user interface and a controller configured to: operate the electrified powertrain in a normal regeneration mode associated with a first electric regeneration and vehicle deceleration rate or a maximum regeneration mode associated with a second, greater electric regeneration and vehicle deceleration rate; receive input from a driver of the vehicle via the user interface indicating a request to enable the maximum regeneration mode; detect a status of the maximum regeneration mode, wherein the status indicates the availability of the maximum regeneration mode; and in response to receiving the request and based on the status of the maximum regeneration mode and a current vehicle deceleration rate: (i) operate the electrified powertrain in either the maximum regeneration mode or the normal regeneration mode; (ii) selectively output a message to the driver via the user interface indicating the status of the maximum regeneration mode; and (iii) selectively command a hydraulic braking system of the vehicle to generate a braking force based on a driver-intended vehicle deceleration rate associated with the operating regeneration mode.

[0006] In some embodiments, the controller is further configured to control the electrified powertrain to use electrical current generated by conversion of kinetic energy of the electrified powertrain to at least one of: (i) recharge a battery system associated with the at least one electric machine and (ii) power an accessory load of the vehicle, wherein a second electrical regeneration rate of the maximum regeneration mode increases an electric range of the vehicle compared to a first electrical regeneration rate of the normal regeneration mode. In some embodiments, the electrified vehicle is a plug-in hybrid electric vehicle (PHEV).

[0007] In some embodiments, the controller is configured to autonomously command the hydraulic brake system to apply the hydraulic brake to generate the braking force based on a driver-expected vehicle deceleration rate associated with the regeneration mode in operation and without requiring any driver input via a brake pedal of the vehicle. In some embodiments, the controller is further configured to autonomously command the hydraulic brake system to generate additional hydraulic brake pressure with a vacuum-independent electric brake booster and provide it to the hydraulic brake to thereby generate the braking force based on the driver-expected vehicle deceleration rate associated with the regeneration mode in operation and without requiring any driver input via the brake pedal.

[0008] In some embodiments, when the status indicates that the maximum regeneration mode is available, the controller is further configured to: determine whether the engine is connected to a transmission of the electrified vehicle, operate the electrified powertrain such that kinetic energy at the engine and the at least one electric machine is collectively converted to electrical energy at the second regeneration rate when the engine and the transmission are connected, and operate the electrified powertrain such that kinetic energy at the at least one electric machine is converted to electrical energy at the second regeneration rate when the engine and the transmission are disconnected.

[0009] In some embodiments, the controller is configured to determine the status of the maximum regeneration mode based on: (i) whether there is a fault of the vehicle that would limit the maximum regeneration mode, (ii) whether the fault of the vehicle is recoverable, and (iii) whether the fault of the vehicle has been recovered when the fault of the vehicle is recoverable. In some embodiments, when the fault of the vehicle is not recoverable and the current vehicle deceleration rate is less than the first vehicle deceleration rate, the controller is further configured to: start the engine when the engine is off, operate the electrified powertrain in the normal regeneration mode such that kinetic energy at the engine and the at least one electric machine is collectively converted to electrical energy at the first regeneration rate and the current deceleration rate of the vehicle is increased, output a message to the driver via a user interface indicating that the maximum regeneration mode is not available, and selectively command the hydraulic brake system to generate the braking force based on a driver-expected vehicle deceleration rate associated with the regeneration mode in operation and without requiring any driver input via a brake pedal of the vehicle.

[0010] In some embodiments, when the vehicle malfunction is recoverable and has been recovered, the controller is further configured to: operate the electrified powertrain in the maximum regenerative mode such that kinetic energy at the engine and the at least one electric machine is collectively converted to electrical energy at a second regenerative rate, and output a message to the driver via the user interface indicating that the maximum regenerative mode is available. In some embodiments, when the vehicle malfunction is recoverable but has not been recovered, the controller is further configured to: operate the electrified powertrain in the normal regenerative mode such that kinetic energy at the engine and the at least one electric machine is collectively converted to electrical energy at a first regenerative rate, and output a message to the driver via the user interface indicating that the maximum regenerative mode is temporarily unavailable.

[0011] According to another example aspect of the present disclosure, a method for electrical regenerative and vehicle deceleration control for an electrified vehicle having an electrified powertrain including an engine and at least one electric machine is presented. In one example embodiment, the method includes: operating, by a controller of the electrified vehicle, the electrified powertrain in either a normal regenerative mode associated with a first electrical regenerative and vehicle deceleration rate or a maximum regenerative mode associated with a greater second electrical regenerative and vehicle deceleration rate, receiving, by the controller and from a driver of the vehicle via a user interface, an input indicative of a request to enable the maximum regenerative mode, detecting, by the controller, a status of the maximum regenerative mode, wherein the status is indicative of availability of the maximum regenerative mode, and in response to receiving the request and based on the status of the maximum regenerative mode and a current vehicle deceleration rate: (i) operating, by the controller, the electrified powertrain in either the maximum regenerative mode or the normal regenerative mode, (ii) selectively outputting, by the controller and via the user interface, a message indicative of the status of the maximum regenerative mode to the driver, and (iii) selectively commanding, by the controller, a hydraulic brake system of the vehicle to generate a braking force based on a vehicle deceleration rate expected by the driver associated with the regenerative mode in operation.

[0012] In some embodiments, the method further includes controlling the electrified powertrain to use electrical current generated by converting kinetic energy of the electrified powertrain to at least one of: (i) recharge a battery system associated with the at least one electric machine and (ii) power an accessory load of the vehicle, wherein the second electrical regenerative rate of the maximum regenerative mode increases an electric-only range of the vehicle compared to the first electrical regenerative rate of the normal regenerative mode. In some embodiments, the electrified vehicle is a PHEV.

[0013] In some embodiments, selectively commanding the hydraulic brake system includes commanding the hydraulic brake system to apply the hydraulic brake to generate the braking force based on a driver-expected vehicle deceleration rate associated with the regenerative mode in operation and without requiring any driver input via the vehicle brake pedal. In some embodiments, selectively commanding the hydraulic brake system further includes autonomously commanding the hydraulic brake system to generate additional hydraulic brake pressure with a vacuum-independent electric brake booster and provide it to the hydraulic brake to thereby generate the braking force based on the driver-expected vehicle deceleration rate associated with the regenerative mode in operation and without requiring any driver input via the brake pedal.

[0014] In some embodiments, when the status indicates that the maximum regenerative mode is available, the method further includes determining, by the controller, whether the engine is connected to a transmission of the electrified vehicle, operating, by the controller, the electrified powertrain such that kinetic energy at the engine and the at least one electric machine is collectively converted to electrical energy at the second regenerative rate when the engine and the transmission are connected, and operating, by the controller, the electrified powertrain such that kinetic energy at the at least one electric machine is converted to electrical energy at the second regenerative rate when the engine and the transmission are disconnected.

[0015] In some embodiments, determining the status of the maximum regenerative mode is based on (i) whether there is a fault of the vehicle that would limit the maximum regenerative mode, (ii) whether the vehicle fault is recoverable, and (iii) whether the vehicle fault has been recovered when the vehicle fault is recoverable. In some embodiments, when the vehicle fault is not recoverable and the current vehicle deceleration rate is less than the first vehicle deceleration rate, the method further includes starting, by the controller, the engine when the engine is off, operating, by the controller, the electrified powertrain in the normal regenerative mode such that kinetic energy at the engine and the at least one electric machine is collectively converted to electrical energy at the first regenerative rate and the current deceleration rate of the vehicle is increased, outputting, by the controller and via a user interface, a message to the driver indicating that the maximum regenerative mode is not available, and selectively commanding, by the controller, the hydraulic brake system to generate the braking force based on a driver-expected vehicle deceleration rate associated with the regenerative mode in operation and without requiring any driver input via the vehicle brake pedal.

[0016] In some embodiments, when the vehicle malfunction is recoverable and has been recovered, the method further comprises operating, by the controller, the electrified powertrain in a maximum regenerative mode such that kinetic energy at the engine and the at least one electric machine is collectively converted to electrical energy at a second regenerative rate, and outputting, by the controller and via the user interface, a message to the driver indicating that the maximum regenerative mode is available. In some embodiments, when the vehicle malfunction is recoverable but has not been recovered, the controller is further configured to operate, by the controller, the electrified powertrain in a normal regenerative mode such that kinetic energy at the engine and the at least one electric machine is collectively converted to electrical energy at a first regenerative rate, and outputting, by the controller and via the user interface, information to the driver indicating that the maximum regenerative mode is temporarily unavailable.

[0017] The applicability of the teachings of the present disclosure in other fields of endeavor will become apparent from the description provided hereinafter, from the appended claims, and from the accompanying drawings of which the same figures in several of the drawings represent the same features. It should be appreciated that the detailed description, including the embodiments and drawings referenced therein, are merely exemplary in nature and are intended to illustrate, but not limit the scope of the disclosure, its application or use. Thus, variations that do not depart from the spirit of the disclosure are intended to be within the scope of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a functional block diagram of an electrified vehicle including an electric regenerative and vehicle deceleration control system in accordance with the principles of the present disclosure; and

[0019] Figure 2 is a flowchart of an example electric regenerative and vehicle deceleration control method for an electrified vehicle in accordance with the principles of the present disclosure. DETAILED DESCRIPTION

[0020] As previously mentioned, conventional electric regenerative systems on electrified vehicles suffer from having only a single regenerative rate, which can not be optimal, and also fail to provide the driver of the vehicle with the expected rate or feel of deceleration when the electric regenerative system fails or is otherwise unavailable, e.g., due to other vehicle malfunctions that would prevent or otherwise limit or inhibit operation of the electric regenerative system. Accordingly, improved electric regenerative and vehicle deceleration control systems and methods are presented. These systems and methods provide a driver-selectable increased or "max" regenerative mode that converts vehicle kinetic energy to electrical energy at a higher rate than a default or "normal" regenerative mode. In turn, this also provides a higher rate of vehicle deceleration that would be expected by the driver of the vehicle whenever the max regenerative mode is selected. When the max regenerative mode is unavailable, driver notification can be provided via a user interface regarding the status of the max regenerative mode and other actions that can be taken, e.g., to control the electrified powertrain and / or to autonomously apply the hydraulic brake system to provide the rate of vehicle deceleration expected by the driver, and without the driver having to depress the brake pedal of the vehicle. Potential benefits include increased electric range and improved driver experience for the electrified vehicle, as the driver will always experience the rate of vehicle deceleration that he / she expects.

[0021] Reference is now made to Figure 1FIG. 1 shows a functional block diagram of an electrified vehicle 100 having an example electric regenerative and vehicle deceleration control system, in accordance with the principles of the present disclosure. In one example implementation, the electrified vehicle 100 is a plug-in hybrid electric vehicle (PHEV), although it should be appreciated that the electrified vehicle 100 can be any suitable electrified vehicle. The electrified vehicle 100 includes an electrified powertrain 104 that includes an internal combustion engine 108 and one or more electric machines 112 that are powered by a battery system 116 and collectively generate drive torque that is transmitted through a transmission 120 to a driveline 124 of the electrified vehicle 100 for propulsion. The electrified powertrain 104 is controlled by a controller 128 such that it generates drive torque sufficient to meet a torque request, which can be provided by a driver via one or more driver input devices 132 (e.g., an accelerator pedal 136 having an associated accelerator pedal position sensor 140). It should be appreciated that the controller 128 can include a system having multiple controllers / processors (e.g., an engine controller and a hybrid controller). The driver input devices 132 can further include a brake pedal 144 having an associated brake pedal position sensor 148, as well as a user interface 152 (e.g., a touch display of an infotainment unit) for displaying information to and receiving input from the driver. An electric regenerative system 156, which can be at least partially integrated as part of the electrified powertrain 104, includes one or more electric generators or other energy capture / conversion devices that convert vehicle kinetic energy into electrical energy (e.g., electric current), which can then be used to recharge the battery system 116 and / or power other accessory loads 158 (e.g., pumps, compressors, fans, etc.) of the electrified vehicle 100.

[0022] The electric regenerative system 156 is connected to a combination of the engine 104, the electric machine 112, and the powertrain 124 or components of the hydraulic brake system 160 in order to convert the kinetic energy of the vehicle. The hydraulic brake system 160 generates a braking force that is applied to the powertrain 124 (axles, wheels / tires, etc.) to reduce the speed of the electrified vehicle 100. The hydraulic brake system 160 includes a hydraulic brake 164 that establishes a hydraulic brake pressure therein in response to a depression of the brake pedal 144 by the driver or autonomously in response to a control signal from the controller 128. This hydraulic brake pressure is then used to apply the hydraulic brake 164 to the powertrain 124, thereby creating friction that reduces the speed of the electrified vehicle 100. The hydraulic brake system 160 also includes a vacuum-independent electric brake booster 168. The electric brake booster 168 is vacuum-independent in that it can operate independent of engine vacuum and is therefore able to operate under any engine operating conditions. The electric brake booster 168 generates additional hydraulic brake pressure for the hydraulic brake 164, thereby enabling the hydraulic brake 164 to provide greater braking force at the powertrain 124. The electric brake booster 168 can be critical to the technology of the present disclosure because there can be instances in which the hydraulic brake 164 by itself cannot provide enough braking force to achieve the vehicle deceleration rate intended by the driver. Furthermore, the electric brake booster 168 is much faster or much more sensitive in response (e.g., four times faster) compared to a conventional electronic stability control (ESC) system that could alternatively be used to provide additional braking capability. The electrified vehicle 100 can also include one or more other sensors 172 for sensing various vehicle / powertrain operating parameters, such as a vehicle speed sensor and speed / temperature / pressure / status (e.g., state of charge or SOC) sensors of components of the electrified powertrain 104 (engine 108, electric machine 112, battery system 116, etc.).

[0023] The controller 128 is also configured to perform at least a portion of the electric regenerative and vehicle deceleration control techniques of the present disclosure. This includes operating the vehicle 100 or electrified powertrain 104 in a default or "normal" regenerative mode, or operating the vehicle 100 or electrified powertrain 104 in an increased or "maximum" regenerative mode in response to a driver input. It should be understood that the phrase "maximum regenerative mode" as used herein can refer to any regenerative mode that generates additional electrical energy and results in a greater rate of vehicle deceleration than the normal regenerative mode. It should also be understood that there can be a variety of different increased regenerative modes that have different levels of electrical energy generation and result in different rates of vehicle deceleration, and that the highest or most aggressive one of these can be referred to as the maximum regenerative mode. The maximum regenerative mode can be utilized to increase recharging of the battery system 116 in addition to generating additional electrical energy as compared to the normal regenerative mode, whereby the electric range of the electrified vehicle 100 can be extended. The distribution or separation between kinetic energy converted from the engine 108 and kinetic energy converted from the electric machine 112 can be intelligently determined in real-time based on, for example, speed / temperature / pressure / state measurements by sensors 172 of components of the electrified powertrain 104.

[0024] Because the maximum regenerative mode is driver-selectable, the driver can enable the mode by, for example, providing an input (e.g., a touch input of a button or icon) via the user interface 152. In doing so, the driver knows that his / her selection, and will expect a rate of vehicle deceleration consistent with the maximum regenerative mode. However, in some scenarios, this maximum regenerative mode can not be available. Accordingly, the controller 128 determines a status of the maximum regenerative mode. There can be various vehicle malfunctions that can inhibit or otherwise limit maximum regenerative mode operation, including but not limited to controller / processor malfunctions, memory malfunctions, and component malfunctions (electrified powertrain 104, electric regenerative system 156, hydraulic brake system 160, etc.). This detected "status" of the maximum regenerative mode thus indicates the current availability of the maximum regenerative mode. However, some vehicle malfunctions are recoverable. For example, a diagnosis can be performed to detect that the vehicle malfunction no longer exists, or some treatment or conditioning routine can be expected to recover the vehicle malfunction. Accordingly, the status of the maximum regenerative mode can change depending on whether the vehicle malfunction is recoverable.

[0025] Reference is now made to Figure 2 and with continued reference to Figure 1, showing a flowchart of an example electric regenerative and vehicle deceleration control method 200 for an electrified vehicle (e.g., electrified vehicle 100) in accordance with the principles of the present disclosure. At 204, controller 128 determines whether electrified vehicle 100 is currently experiencing a deceleration or “coast” event. For example, this can be in response to an accelerator pedal 136 (e.g., as measured by sensor 140) not being depressed (or less than a depression threshold) and a brake pedal 144 (e.g., as measured by sensor 148) not being depressed (or less than a depression threshold). Vehicle speed (e.g., from sensor 172) can also be taken into account. In some cases, this can trigger a deceleration fuel shutoff (DFSO) event, in which fuel supply to engine 108 is temporarily suspended, but it should also be appreciated that engine 108 can continue to run (e.g., to provide additional kinetic energy for conversion to electrical energy, and in turn, more vehicle deceleration). When vehicle deceleration / coasting is not occurring, neither normal regenerative nor maximum regenerative modes are enabled at 208, and no vehicle deceleration control occurs, and method 200 ends or returns. However, when vehicle deceleration / coasting is occurring, method 200 proceeds to 212. At 212, controller 128 determines whether a request to enable maximum regenerative mode has been received from the driver (e.g., via user interface 152). When a maximum regenerative mode request has not been received, controller 128 operates electrified powertrain 104 in normal regenerative mode at 216, and method 200 ends or returns.

[0026] When a maximum regenerative mode has been received, method 200 proceeds to 220. Based on the status of the maximum regenerative mode and the current deceleration of electrified vehicle 100 (e.g., based on measurements from sensors 172 such as a vehicle speed sensor), controller 128 is then configured to perform various different operations. At 220, controller 128 determines whether there is a vehicle fault that would prevent or otherwise limit or inhibit operation of the maximum regenerative mode. This is also described herein as controller 128 determining a part of the status of the maximum regenerative mode indicative of its availability. When there is no vehicle fault, controller 128 determines at 224 whether engine 108 and transmission 120 are connected (e.g., via a hydrodynamic coupling or torque converter). When disconnected, controller 128 controls electrified powertrain 104 at 228 such that only electric machine 112 provides kinetic energy that is converted to electrical energy by electric regenerative system 156 to achieve a higher (second) rate of regeneration and a higher (second) rate of vehicle deceleration, and method 200 ends or returns. When connected, controller 128 controls electrified powertrain 104 at 232 such that engine 108 and electric machine 112 collectively provide (e.g., in some optimal split manner) kinetic energy that is converted to electrical energy by electric regenerative system 156 at a similar level / rate as described with respect to 228, and method 200 ends or returns.

[0027] At 236, when a vehicle fault is detected, the controller 128 determines whether the vehicle fault is recoverable. When the vehicle fault is not recoverable and the current vehicle deceleration rate is less than the vehicle deceleration rate associated with the normal regenerative mode, the method 200 proceeds to 240. At 240, the controller 128 is configured to perform the following steps: (i) start the engine 108 (e.g., because the electrified powertrain 104 is desired to provide as much kinetic energy conversion and vehicle deceleration as possible) when the engine 108 is off (e.g., due to a previous DFSO event), (ii) output a message (e.g., via the user interface 152) to the driver indicating that the maximum regenerative mode is not available. In addition, the controller 128 is also configured to autonomously apply the hydraulic brake system 160 to provide any additional vehicle deceleration needed to achieve the driver-expected vehicle deceleration rate associated with the normal regenerative mode. In some cases, this will involve the electric brake booster 168 providing quick additional hydraulic brake pressure to the hydraulic brakes 164 because the hydraulic brakes 164 cannot provide enough braking force to achieve the driver-expected vehicle deceleration rate. The method 200 then ends or returns.

[0028] At 236, when the vehicle fault is recoverable, the method 200 proceeds to 244, where the controller 128 determines whether the vehicle fault has recovered. When the vehicle fault has recovered, the method 200 proceeds to 248. At 248, the controller 128 is configured to operate the electrified powertrain 104 in the normal regenerative mode, as previously described herein, and is also configured to output a message to the driver of the electrified vehicle 104 (e.g., via the user interface 152) that the maximum regenerative mode is temporarily not available, which provides the driver with sufficient notice that the vehicle deceleration rate associated with the normal regenerative mode should be expected. It should be noted that this driver message indicates that the maximum regenerative mode is temporarily not available because the vehicle fault can subsequently recover and then the maximum regenerative mode can be available and enabled. After 248, the method 200 can end / return or directly return to 244 and wait to see if the vehicle fault recovers. When the vehicle fault has recovered, the method 200 proceeds from 244 to 252. At 252, the controller 128 is configured to operate the electrified powertrain 104 in the maximum regenerative mode (similar to that described above with respect to the maximum regenerative mode, depending on whether the engine 108 and transmission 120 are connected), and the controller 128 is also configured to output a message to the driver of the electrified vehicle 100 (e.g., via the user interface 152) that the maximum regenerative mode is available and is currently operating. Similar to the other messages described above, this message can provide the driver with sufficient notice as to what level of vehicle deceleration can be expected (e.g., because the fault can have been unavailable and temporarily unavailable prior to the vehicle fault recovering). The method 200 then ends or returns.

[0029] It should be understood that the term“controller” as used herein refers to any suitable control device or collection of control devices configured to perform at least a portion of the techniques of the present disclosure. Non-limiting examples include an application-specific integrated circuit (ASIC), one or more processors, and a non-transitory memory having instructions stored thereon that, when executed by the one or more processors, cause the controller to perform a set of operations corresponding to at least a portion of the techniques of the present disclosure. The one or more processors can be a single processor or two or more processors operating in parallel or in a distributed architecture.

[0030] It should be understood that mix and match of features, elements, methods, and / or functions between various examples can be expressly contemplated herein so that one of skill in the art will understand from the teachings herein that features, elements, and / or functions from one example can be combined with features, elements, and / or functions from another example as appropriate, unless described otherwise above.

Claims

1. An electric regenerative and vehicle deceleration control system for an electrified vehicle having an electrified powertrain comprising an engine and at least one electric machine, the control system comprising: a user interface; and a controller configured to: operate the electrified powertrain in either a normal regenerative mode associated with a first electric regenerative rate and a first vehicle deceleration rate or a maximum regenerative mode associated with a second electric regenerative rate and a second vehicle deceleration rate, the second electric regenerative rate and the second vehicle deceleration rate being greater than the first electric regenerative rate and the first vehicle deceleration rate, respectively; receive, via the user interface, an input from a driver of the vehicle indicative of a request to enable the maximum regenerative mode; detect a status of the maximum regenerative mode, wherein the status is indicative of availability of the maximum regenerative mode; and in response to receiving the request and based on the status of the maximum regenerative mode and a current vehicle deceleration rate: (i) operate the electrified powertrain in either the maximum regenerative mode or the normal regenerative mode; (ii) selectively output, via the user interface, a message to the driver indicative of the status of the maximum regenerative mode; and (iii) selectively command a hydraulic brake system of the vehicle to generate a brake force based on a driver-expected vehicle deceleration rate associated with the regenerative mode in operation, wherein the controller is further configured to autonomously command the hydraulic brake system to apply the hydraulic brake system to generate the brake force based on the driver-expected vehicle deceleration rate associated with the regenerative mode in operation and without requiring any driver input via a brake pedal of the vehicle, and wherein the controller is further configured to autonomously command the hydraulic brake system to generate additional hydraulic brake pressure with a vacuum-independent electric brake booster and provide it to the hydraulic brake system to thereby generate the brake force based on the driver-expected vehicle deceleration rate associated with the regenerative mode in operation and without requiring any driver input via the brake pedal. the controller is further configured to control the electrified powertrain to use electric current generated by conversion of kinetic energy of the electrified powertrain to at least one of (i) recharge a battery system associated with the at least one electric machine and (ii) power an accessory load of the vehicle, 2. The control system of claim 1, wherein, wherein the second electric regenerative rate of the maximum regenerative mode increases electric range of the vehicle compared to the first electric regenerative rate of the normal regenerative mode. when the status indicates that the maximum regenerative mode is available for use, the controller is further configured to:

3. The control system of claim 1, wherein, determine whether the engine is connected to a transmission of the electrified vehicle; when the engine is connected to the transmission, operate the electrified powertrain such that kinetic energy at the engine and the at least one electric machine is collectively converted to electric energy at the second electric regenerative rate; and ​ ​ when the engine is disconnected from the transmission, operating the electrified powertrain such that kinetic energy at the at least one electric machine is converted to electrical energy at the second electrical regeneration rate.

4. The control system of claim 1, wherein, the controller is configured to determine the status of the maximum regeneration mode based on: (i) whether there is a fault of the vehicle that will limit the maximum regeneration mode, (ii) whether the vehicle fault is recoverable, and (iii) when the vehicle fault is recoverable, whether the vehicle fault has been recovered.

5. The control system of claim 4, wherein, when the vehicle fault is not recoverable and a current vehicle deceleration rate is less than the first vehicle deceleration rate, the controller is further configured to: start the engine when the engine is off; operate the electrified powertrain in the normal regeneration mode such that kinetic energy at the engine and the at least one electric machine is collectively converted to electrical energy at the first electrical regeneration rate and a current deceleration rate of the vehicle is increased; output, via the user interface, a message to the driver indicating that the maximum regeneration mode is not available; and selectively command the hydraulic brake system to generate the brake force based on the driver-expected vehicle deceleration rate associated with the regeneration mode in operation and without requiring any driver input via a brake pedal of the vehicle.

6. The control system of claim 4, wherein, when the vehicle fault is recoverable and has been recovered, the controller is further configured to: operate the electrified powertrain in the maximum regeneration mode such that kinetic energy at the engine and the at least one electric machine is collectively converted to electrical energy at the second electrical regeneration rate; and output, via the user interface, a message to the driver indicating that the maximum regeneration mode is available.

7. The control system of claim 4, wherein, when the vehicle fault is recoverable but has not been recovered, the controller is further configured to: operate the electrified powertrain in the normal regeneration mode such that kinetic energy at the engine and the at least one electric machine is collectively converted to electrical energy at the first electrical regeneration rate; and output, via the user interface, a message to the driver indicating that the maximum regeneration mode is temporarily not available.

8. The control system of claim 1, wherein, the electrified vehicle is a plug-in hybrid electric vehicle (PHEV).

9. A method of electrical regeneration and vehicle deceleration control for an electrified vehicle having an electrified powertrain including an engine and at least one electric machine, the method comprising: operating, by a controller of the electrified vehicle, the electrified powertrain in either a normal regeneration mode associated with a first electrical regeneration rate and a first vehicle deceleration rate or a maximum regeneration mode associated with a second electrical regeneration rate and a second vehicle deceleration rate, the second electrical regeneration rate and the second vehicle deceleration rate being greater than the first electrical regeneration rate and the first vehicle deceleration rate, respectively; receiving, by the controller and via a user interface, an input from a driver of the vehicle indicating a request to enable the maximum regeneration mode; detecting, by the controller, a status of the maximum regeneration mode, wherein the status indicates an availability of the maximum regeneration mode; and selectively commanding, by the controller, the hydraulic brake system to generate the brake force based on the driver-expected vehicle deceleration rate associated with the regeneration mode in operation and without requiring any driver input via a brake pedal of the vehicle. in response to receiving the request and based on a status of the maximum regenerative mode and a current vehicle deceleration rate: (i) operating, by the controller, the electrified powertrain in the maximum regenerative mode or the normal regenerative mode; (ii) selectively outputting, by the controller and via the user interface, a message indicative of the status of the maximum regenerative mode to the driver; and (iii) selectively commanding, by the controller, a hydraulic brake system of the vehicle to generate a braking force based on a driver-expected vehicle deceleration rate associated with the regenerative mode in operation, wherein selectively commanding the hydraulic brake system includes commanding the hydraulic brake system to apply the hydraulic brake system to generate the braking force based on the driver-expected vehicle deceleration rate associated with the regenerative mode in operation and without requiring any driver input via a brake pedal of the vehicle, and wherein selectively commanding the hydraulic brake system further includes autonomously commanding the hydraulic brake system to generate additional hydraulic brake pressure with a vacuum-independent electric brake booster and provide the additional hydraulic brake pressure to the hydraulic brake system to thereby generate the braking force based on the driver-expected vehicle deceleration rate associated with the regenerative mode in operation and without requiring any driver input via the brake pedal.

10. The method of claim 9, further comprising controlling the electrified powertrain to use electrical current generated by conversion of kinetic energy of the electrified powertrain to at least one of (i) recharge a battery system associated with the at least one electric machine and (ii) power an accessory load of the vehicle, wherein the second electrical regenerative rate of the maximum regenerative mode is increased over a first electrical regenerative rate of the normal regenerative mode to increase electric range of the vehicle.

11. The method of claim 9, wherein, when the status indicates that the maximum regenerative mode is available for use, the method further comprises: determining, by the controller, whether the engine is connected to a transmission of the electrified vehicle; when the engine is connected to the transmission, operating, by the controller, the electrified powertrain such that kinetic energy at the engine and the at least one electric machine is collectively converted to electrical energy at the second electrical regenerative rate; and when the engine is disconnected from the transmission, operating, by the controller, the electrified powertrain such that kinetic energy at the at least one electric machine is converted to electrical energy at the second electrical regenerative rate.

12. The method of claim 9, wherein, determining the status of the maximum regenerative mode is based on (i) whether there is a fault of the vehicle that would limit the maximum regenerative mode, (ii) whether the vehicle fault is recoverable, and (iii) whether the vehicle fault has been recovered when the vehicle fault is recoverable.

13. The method of claim 12, wherein, when the vehicle fault is not recoverable and the current vehicle deceleration rate is less than the first vehicle deceleration rate, the method further comprises: starting, by the controller, the engine when the engine is off; operating, by the controller, the electrified powertrain in the normal regenerative mode such that kinetic energy at the engine and the at least one electric machine is collectively converted into electrical energy at the first electric regenerative rate, and a current rate of deceleration of the vehicle is increased; outputting, by the controller and via the user interface, information indicating that the maximum regenerative mode is not available to the driver; and selectively commanding, by the controller, the hydraulic brake system to generate the brake force based on the driver-expected rate of vehicle deceleration associated with the regenerative mode in operation and without requiring any driver input via a brake pedal of the vehicle.

14. The method of claim 12, wherein, when the vehicle malfunction is recoverable and has been recovered, the method further comprises: operating, by the controller, the electrified powertrain in the maximum regenerative mode such that kinetic energy at the engine and the at least one electric machine is collectively converted into electrical energy at the second electric regenerative rate; and outputting, by the controller and via the user interface, a message indicating that the maximum regenerative mode is available to the driver.

15. The method of claim 12, wherein, when the vehicle malfunction is recoverable but has not yet been recovered, the controller is further configured to: operating, by the controller, the electrified powertrain in the normal regenerative mode such that kinetic energy at the engine and the at least one electric machine is collectively converted into electrical energy at the first electric regenerative rate; and outputting, by the controller and via the user interface, a message indicating that the maximum regenerative mode is temporarily not available to the driver.

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