Claims:We Claim:
1. A three-wheeler electric vehicle having a creep mode, comprising:
i. a motor for applying torque to the rear wheels;
ii. a battery pack for supplying voltage to the motor for generating torque;
iii. an accelerator pedal for controlling the torque applied to the wheels;
iv. a brake pedal for halting the wheels in motion;
v. an electric vehicle controller for controlling operation of the vehicle;
vi. a motor control unit for controlling the speed of the motor;
wherein,
o a brake switch detects depression of the brake pedal;
o a direction selector switch analyzes the neutral mode in the vehicle;
o a motor speed encoder analyzes the speed of motor rotation; and
o a software module configured in the electric vehicle controller controls the creep mode in the three-wheeler electric vehicle.

2. A method for implementing creep mode in the three wheeler electric vehicle, comprising the following steps:
i. the creep mode of the vehicle assesses that the speed of the vehicle is zero;
ii. the creep mode of the vehicle analyzes that the vehicle is not in neutral or parking mode; and
iii. the creep mode of the vehicle is activated on detecting depression of brake pedal in the vehicle.

3. The method for implementing creep mode in the three wheeler electric vehicle as claimed in claim 2, wherein the vehicle is in an “Idle Mode” during normal condition.

4. The method for implementing creep mode in the three wheeler electric vehicle as claimed in claim 2, wherein on detecting depression on the brake pedal “Creep Mode” is enabled.

5. The method for implementing creep mode in the three wheeler electric vehicle as claimed in claim 2, wherein the direction selector switch simultaneously analyzes if the vehicle is not in neutral or parking mode.

6. The method for implementing creep mode in the three wheeler electric vehicle as claimed in claim 2, wherein the brake pedal is released by the user for the vehicle movement at fixed speed.

7. The method for implementing creep mode in the three wheeler electric vehicle as claimed in claim 2, wherein the speed of the rotation of the motor of the vehicle is detected through the motor speed encoder.

8. The method for implementing creep mode in the three wheeler electric vehicle as claimed in claim 2, wherein the speed with which the motor is rotating is controlled through electric vehicle controller .

9. The method for implementing creep mode in the three wheeler electric vehicle as claimed in claim 2, wherein the “Creep Mode” is deactivated when the user presses the accelerator pedal.

10. The method for implementing creep mode in the three wheeler electric vehicle as claimed in claim 2, wherein on deactivating the “Creep Mode” the vehicle resumes movement in the “Idle Mode”.
, Description:FIELD OF INVENTION
[001] The present invention relates to a lightweight control strategy for implementation of creep function in a three wheeler electric vehicle. Particularly, the present invention provides a system and method for optimizing the torque and speed of the electric vehicle at the time of navigating the vehicle through a crowded/public area or any other slow-speed situations where a steady speed is required.
BACKGROUND OF THE INVENTION
[002] E-Mobility due to their efficient and different capabilities are receiving considerable attention as a substitute for conventional vehicles. Primarily, because electric vehicles have good environmental protection performance, and they are also considered as green transportation. Therefore, need for an electric vehicle is on the rise in every field, be it a four wheeler, three wheeler or two wheelers. Further, electric three-wheelers or e-rickshaws that have become the face of electric mobility in India presently. A need for an economic and greener solution has led to the development of electric three wheeler rickshaws. As three wheelers are now available at almost every location, there are various problems associated with such vehicles that have been encountered.
[003] While traveling, there are numerous instances where the vehicle must stop before a destination is reached for e.g., the vehicle stops at traffic signals, cross-walks, stop signs and the like. Continuously regulating the vehicle’s throttle in tight spaces such as in traffic or while parking the vehicle is a tedious work. Further, for a driver standing in traffic, it is difficult to control the vehicle where there is continuous release and pressing of acceleration and brake pedal. To maintain the steady speed of the vehicle, the driver has to remain vigilant on the road as well as maintain the balance between the acceleration and brake pedal. Sometimes the balance between the brake pedal and acceleration pedal is not maintained and this leads to unwanted accidents.
[004] US Patent US8814750B2 relates to a control module including a traffic determination module that determines when a vehicle is in traffic and that selectively generates a traffic signal. The control module has a creep enable module that generates a creep enable signal based on the traffic signal. The control module further includes a power control module that selectively generates an internal combustion engine disable signal. The power control module also commands a motor generator unit to produce power based on the creep enable signal as a driver reduces brake pedal pressure. However, the cited prior art document discloses about the control function inbuilt in a four wheeler vehicle and not that on a three wheeler.
[005] Hence, with respect to the problem encountered above, there is a need for a technology that provides driver assistance at the time of controlling a three wheeler vehicle in a traffic which is economic as well.
OBJECTIVE OF THE INVENTION
[006] The primary objective of the present invention is to provide a system and method for implementing a creep control functionality in a three-wheeler electric vehicle.
[007] Yet another objective of the present invention is to optimize the torque and speed of a three wheeler electric vehicle to maintain an ideal speed of the vehicle at the time of movement in traffic and provide assistance to the driver while driving.
[008] Yet another objective of the present invention is to provide an economic solution to detect movement of a three wheeler vehicle in traffic and provide assistance.
[009] Other objectives and advantages of the present invention will become apparent from the following description taken in connection with the accompanying drawings, wherein, by way of illustration and example, the aspects of the present invention are disclosed.
BRIEF DESCRIPTION OF DRAWINGS
[0010] The present invention will be better understood after reading the following detailed description of the presently preferred aspects thereof with reference to the appended drawings, in which the features, other aspects and advantages of certain exemplary embodiments of the invention will be more apparent from the accompanying drawing in which:
[0011] Figure 1 illustrates the system diagram of an electric three-wheeler vehicle;
[0012] Figure 2 illustrates a flowchart of working of the creep mode in an electric three-wheeler vehicle in an incline position.
SUMMARY OF THE INVENTION
[0013] The present invention provides a system and method for implementing the creep control function in a three-wheeler electric vehicle. Particularly, the present invention discloses a feature that assists the user while driving amidst the traffic and while the user switches between the brake and acceleration pedals. The creep mode assists in maintaining a limited torque and speed of the three wheeler vehicle in the direction selected by the user. Once the user presses the accelerator pedal, it releases the creep mode. In the present invention, creep mode only provides assistance i.e., maintain an ideal slow speed of the vehicle and does not increase the traction, it just provides assistance to the user while driving the vehicle in a traffic.
DETAILED DESCRIPTION OF THE INVENTION
[0014] The following detailed description and embodiments set forth herein below are merely exemplary out of the wide variety and arrangement of instructions which can be employed with the present invention. The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. All the features disclosed in this specification may be replaced by similar other or alternative features performing similar or same or equivalent purposes. Thus, unless expressly stated otherwise, they all are within the scope of the present invention.
[0015] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
[0016] The terms and words used in the following description and claims are not limited to the bibliographical meanings but are merely used to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention.
[0017] It is to be understood that the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.
[0018] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps, or components but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.
[0019] It should be understood that the present invention is specifically directed towards the implementation of the technology in three wheeler electric vehicles however, the technology can also be implemented in other types of hybrid or non-hybrid electric vehicles.
[0020] The present invention provides a lightweight control strategy for implementing the creep mode in an electric three-wheeler vehicle. Particularly the present invention discloses a feature that assists the user of a three wheeler electric vehicle while the user fails to maintain balance between the brake and acceleration pedals at the time of driving the vehicle amidst the traffic. The method comprises of two modes i.e. “Idle Mode” (100) and “Creep Mode” (101).
[0021] In the present invention, Figure 1 generally depicts a system for carrying out the method for providing assistance to the user driving an electric vehicle while moving in a crowded area according to one embodiment described herein. The system and method provide assistance in maintaining an ideal slow speed of the vehicle via automatic application of torque and speed in forward direction, thereby reducing wear on mechanical braking components and also pressure on the driver for maintaining a slow speed while travelling in a crowded area or any other such applications where a constant slow speed is required. The system for enabling the creep mode in an electric vehicle comprises an electric vehicle controller incorporating an electric vehicle controller and motor control unit operatively connected with an electric motor/generator, a high voltage battery pack, a direction selector switch, a brake switch, and motor speed encoder. In an embodiment each of these elements and the operation of the system will be described in more detail herein:
[0022] (a) Electric Motor: In an aspect, the electric motor/generator provides the ignition power for the vehicle. In the present invention, a high speed torque motor is utilized, and preferably a three phase air-cooled induction motor is utilized as prime mover providing the forward moving torque. As per a preferred embodiment, specifications of the motor being utilized for ignition are:
Peak Power: 9 kW
Peak Torque: 45 Nm
RPM Range: 0 to 10,000 rpm
Battery Pack Voltage: 48V
[0023] (b) Electric Vehicle Controller : It is a main component of an Electric Vehicle (EV) which controls the major operation in the vehicle. The electric vehicle controller is further divided into two section:
(i) Power Board: It is an array of plurality of power electronic devices which helps in generating three phase supply for the induction motor via the direct (DC) power obtained from the battery having capacity at least 48 V.
(ii) Control Board: A microcontroller based control board which performs all the control function in the vehicle from motor control to vehicle control.
[0024] (c) Battery Pack: It is a power storing device having a capacity of at least 48 volts. It is the only power storage device fitted in the vehicle. A voltage sensor and current sensor may be electronically connected to the high voltage battery to control the charging and discharging of the high voltage battery.
[0025] (d) RNFB Switch: According to an embodiment, a Direction Selector Switch is also referred as the RNFB Switch. The switch is operated by the user to select whether he wants to drive vehicle in forward direction (F), reverse direction (R), in boost mode (B) or want to keep in idle in neutral mode (N). The switch is interconnected with electric vehicle controller . It is a digital input knob switch which allows the driver to select the vehicle mode of operation from the following:
a. Reverse: If the switch is turned to reverse, vehicle reverse mode is engaged.
b. Neutral: If the switch is turned to neutral, vehicle is put into neutral mode.
c. Forward: If the switch is turned to forward, vehicle moves in forward direction with a power and speed limitation (vehicle power is limited to encourage more driving range).
d. Boost: If the switch is turned to boost, vehicle moves in a forward direction reaching the top speed with no limitation on power.
[0026] (e) Motor Speed Encoder: The Motor Speed Encoder is required for controlling motor. The encoder allows the calculation of the rotation speed of motor (RPMs) and the direction of rotation. The three wheeler vehicle being equipped with a simple single speed gearbox the direction of rotation of the motor determines the direction of rotation of electric vehicle wheels. In the present invention, the motor speed encoder is a bearing based encoder device that can measure the speed and direction of rotation of induction motor. The speed encoder unit produces two signals, at 90 degree phase shift each with resolution of 64 pulse per revolution. The electric vehicle controller receives these two signals via the signal harness and using the Enhanced Quadrature Encoder Pulse (eQEP) module provided in the micro-controller where the signal value is converted into the speed and the direction of the rotation. The speed of rotation is calculated in terms of RPM (Rotation per minute) while the direction is calculated in terms of CW (Clockwise) and CCW (Counter Clockwise) whenever the rotation of the motor shaft changes (technically it is calculated by measuring which of the two signal wave is leading phase wise).
[0027] (g) Software Module: The electric vehicle controller is configured with a software module for controlling the functions of the vehicle built in MATLAB Simulink environment using the generic C20x Simulink support package. The software mode is utilized for controlling the Creep Mode in the three wheeler electric vehicle.
[0028] (h) Brake Switch: According to an embodiment, the brake switch is connected with the brake pedal and evaluates when the brakes are being depressed or released.
[0029] As per an embodiment of the system, for controlling vehicle speed while driving in a crowded area as depicted in Figure 1, the electric vehicle controller is programmed to selectively provide assistance to the vehicle while driving in a traffic or crowded area based on signals received from the motor speed encoder. Based upon input signals received from the encoder the automatic software routine is performed by electric vehicle controller once the depression of the brake is detected, then the creep mode feature is activated by the user. Once the creep mode is enabled, the brakes are released by the user and the three wheeler vehicle starts crawling at a steady or ideal speed of 5Kmph without the user required to actuate the throttle. Electric vehicle Controller keeps a maximum torque demand of TQ_Nom which allows the vehicle to attain a speed of 5Kmph in the direction as defined by the user.
[0030] While the system depicted in Figure 1 is specifically configured for an application of boost in speed, it should be understood that the systems and methods described herein utilizes assistance in speed of the vehicle in the direction chosen by the user to control the speed of an electric three wheeler vehicle while navigating through the crowded area.
[0031] Figure 2 illustrates a flow diagram of one embodiment as per a method in the present invention for providing assistance to navigate the three wheeler electric vehicle through a crowded area without continuously pressing the brake or acceleration pedal. The method may maintain an ideal speed of the three wheeler electric vehicle through the selective control and application of torque in the direction chosen by the user through selector switch for a limited time.
[0032] The flow diagram shown in Figure 2 of the Creep mode shows various states of the system undergoing the creep routine in an electric vehicle. The method is triggered based on the following modes:
(a) Idle Mode (100): When the vehicle is running smoothly, then it is always in the idle mode. Idle mode (100) is the vehicle’s internal state in which it is being piloted by the driver only and is under no automatic software routine. Idle Mode incorporates the following features:
• The ignition of the vehicle is on state,
• the working of the vehicle is controlled through direction selector switch which may be any of the RNFB mode, and
• the vehicle may be stationary or moving via driver’s inputs.
[0033] When the vehicle is switched from the “off” position to the “on” position, the constraints used in the method (e.g., brake release check, speed check and the like) may be initialized prior to the start of the method. Accordingly, an “Idle Mode” (100) condition may exist either when the vehicle ignition is switched off and it is being switched on or when brake pedal has been applied to halt the vehicle. Every 1 millisecond, the internal software module of the present invention continuously monitors to promote to next state by comparing brake position and vehicle speed. If the vehicle is stationary and brake pedal is pressed along with the motor speed being zero, ensuring that the brake sensor is working as a safety check then the method continues on to the “Creep Enable Mode” (101).
[0034] (b) Creep Enable Mode (101): In this state, the software module of present invention checks every millisecond whether the driver is applying the brakes or not. If the software module detects that the brake pedal is depressed, and the motor speed is also equal to zero, then the creep feature in the vehicle is initiated.
[0035] The position of the vehicle brake pedal may be determined based upon a signal received from the brake pedal which is read as a digital input from the brake pedal switch sensor (sensor is essentially a digital switch connected to brake pedal). So, when the brake pedal is not pressed, the electric vehicle controller receives high value from the brake pedal sensor and when the brake pedal is pressed, the sensor gets disengaged, and the electric vehicle controller receives a digital low signal indicating that the brake pedal is pressed. Similarly, the accelerator pedal incorporates an analog sensor to read the functioning of the accelerator pedal. If the vehicle brake pedal is depressed and simultaneously, the direction selector switch analyzes if the vehicle is not in neutral or parking mode, on receiving a positive result electric vehicle controller precedes the method of enabling the creep feature in the electric three wheeler vehicle further. Further the brake pedal is now released for the method to precede . In this mode, once the brake pedal is released, then the three wheeler vehicle starts crawling at a steady speed of 5Kmph. Even the user is not required to press the accelerator pedal. The electric vehicle controller keeps a maximum torque demand of TQ_Nom which allows the vehicle to attain an ideal speed of 5Kmph in the direction as defined by the user. Once the said speed is reached the torque is regulated to maintain the speed. Further, as soon as the acceleration pedal is being pressed by the user the electric three wheeler returns to its Idle Mode (100).
[0036] In an embodiment, the method for implementing creep mode in the three wheeler electric vehicle comprises of the following steps:
• starting the vehicle in “Idle Mode” (100);
• selecting the direction of movement of the vehicle through the direction selector switch by user;
• detecting the direction and speed of the rotation of the wheels of the vehicle through motor speed encoder;
• detecting the depression of the brake pedal through brake switch;
• evaluating the result obtained from brake switch and motor speed encoder;
• activating “Creep Mode (101)” of the vehicle;
• enabling the vehicle to move in the direction selected by the user with the fixed torque; and
• deactivating Creep Mode as the user presses the accelerator pedal.
[0037] The advantages of the system and method of the present invention includes:
• An economic technology for providing assistance to the three wheeler electric vehicle while moving in a crowded area.
• The electric vehicle controller includes the functionality to detect whether the vehicle is in a condition where the user needs assistance while driving in crowded area.
• The creep feature in the vehicle allows the user to smoothly drive the three wheeler vehicle while navigating through crowded or public area.
• The creep feature in the vehicle can allows the user to safely park the vehicle in tight spaces.
[0038] While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.