Claims:WE CLAIM:
1. A method (100) for diagnosing a traction motor of a hybrid type vehicle, the hybrid type vehicle having an internal combustion engine and the traction motor, the method (100) comprising the steps of:
starting the engine, and operating the vehicle in an engine only mode;
measuring a speed of the vehicle, and a voltage generated by a back emf generated in the traction motor;
comparing the back emf generated in the traction motor with a pre-determined value of back emf;
diagnosing a deterioration in the traction motor, if the back emf generated is not within a pre-determined variance of the pre-determined back emf value;
detecting the payload on the vehicle, if the back emf generated is within the pre-determined variance of the pre-determined back emf value;
measuring current in the traction motor, if the payload is not equal to zero; and
determining the quality of the back emf generated, thereby diagnosing condition of the traction motor.

2. The method (100) as claimed in claim 1, further comprising the step of terminating the diagnosis, if the payload is equal to zero.

3. The method (100) as claimed in claim 1, wherein the quality of the back emf generated is determined by a Fast Fourier Transform.

4. The method (100) as claimed in claim 1, wherein the back emf generated in the traction motor is measured by a Voltage Divider Circuit.

5. The method (100) as claimed in claim 1, wherein if the measured current in the traction motor is less than a pre-set no load current value, the condition of the traction motor is diagnosed as having no faults.

6. The method (100) as claimed in claim 1 and 3, wherein if the measured current in the traction motor is greater than the pre-set no load current value, the condition of the traction motor is diagnosed based on prestored data in a Fast Fourier Transform.
, Description:FIELD OF THE INVENTION
[001] The present invention relates to diagnosis of a traction motor in a hybrid type vehicle.

BACKGROUND OF THE INVENTION
[002] Modern hybrid type vehicles have an engine as a primary power source and a traction motor as an auxiliary power source. In traction motors, radial clearance between the stator coils and rotor magnets in a hub mounted motor is a critical gap. The gap is an important parameter in torque generation, efficiency of motor, safety of motor. In these traction motors, the motor rim is a member of unsprung mass and is subjected to high impact loads and the clearance between the stator and rotor is approximately 0.5mm radially. Any variation in this clearance that may be caused due to deformation of stator or rotor or the mechanical connections between stator and rotor. Any resulting change in this clearance can result in malfunctioning or complete failure of the motor.
[003] Specifically in Brushless Type DC motors (BLDC), the stator is connected to stator shaft and magnetic rotor on the hub. One of the critical parameters of the BLDC motor is the air gap throughout the circumference. This air gap needs to be maintained for proper functioning of the motor. In BLDC motors in hybrid vehicles, failures occur due to repeated stress caused while driving which leads to deformation of the motor, for instance, rim deformation. The magnitude of the emf of the BLDC motor depends on magnetic field strength, the air gap, and number of turns on stator coils. The only variables which vary over time are magnetic field strength and the air gap.
[004] Conventionally, for motor diagnosis or prognosis in hybrid type vehicles, systems employing a number of hall sensors have been used. Such conventional systems are expensive, thereby affecting the total price point of the vehicle.
[005] Thus, there is a need in the art for a method for diagnosing a traction motor of a hybrid type vehicle which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION
[006] In one aspect, the present invention is directed towards a method for diagnosing a traction motor of a hybrid type vehicle. The hybrid type vehicle has an internal combustion engine and the traction motor. The method has the steps of: starting the engine, and operating the vehicle in an engine only mode; measuring a speed of the vehicle, and a voltage generated by a back emf generated in the traction motor; comparing the back emf generated in the traction motor with a pre-determined value of back emf; diagnosing a deterioration in the traction motor, if the back emf generated is not within a pre-determined variance of the pre-determined back emf value; detecting the payload on the vehicle, if the back emf generated is within the pre-determined variance of the pre-determined back emf value; measuring current in the traction motor, if the payload is not equal to zero; and determining the quality of the back emf generated, thereby diagnosing condition of the traction motor.
[007] In an embodiment of the invention, the method further has the step of terminating the diagnosis, if the payload is equal to zero.
[008] In a further embodiment of the invention, the quality of the back emf generated is determined by a Fast Fourier Transform.
[009] In a further embodiment of the invention, wherein the back emf generated in the traction motor is measured by a Voltage Divider Circuit.
[010] In another embodiment of the invention, wherein if the measured current in the traction motor is less than a preset no load current value, the condition of the traction motor is diagnosed as having no faults.
[011] In a further embodiment of the invention, if the measured current in the traction motor is greater than the preset no load current value, the condition of the traction motor is diagnosed based on prestored data in a Fast Fourier Transform.

BRIEF DESCRIPTION OF THE DRAWINGS
[012] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 illustrates the method steps involved in a method for diagnosing a traction motor of a hybrid type vehicle, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
[013] The present invention relates to a method of diagnosing a traction motor of a hybrid type vehicle. More particularly, the present invention relates to measuring the back emf of a traction motor to detect any change in the air gap of the motor or chipping of the magnets.
[014] The vehicle as aforementioned has an internal combustion engine that acts as a primary source drives the vehicle. The vehicle further has a battery, a power convertor and a traction motor. In that, the electrically driven traction motor is an auxiliary means of propulsion along with an internal combustion engine. The traction motor converts electrical energy from the battery into mechanical energy to drive the vehicle. The electrical energy supplied to the motor is controlled by a power controller consisting of MOSFETs and microcontrollers.
[015] The traction motor comprises a rotary member referred to as a rotor, and a stationary member referred to as a stator. The stator has lamination stacks and coil windings, and the rotor has one or more magnets which generate magnetic fields. When the coils in the stator are energised through the switching of MOSFET in the power controller, the stator coils generate electromagnetic field through an airgap between the stator and the rotor, thereby generating a torque to drive the vehicle. The magnitude of torque generated and the current consumed depends upon the airgap. Inversely, if a torque is applied to the rotor, an electrical voltage is generated which is termed as a back emf. This results in conversion of mechanical energy into electrical energy. The magnitude of voltage generated depends upon the rpm of the rotor. The back emf generated for a given rpm of the rotor is a characteristic of an electrical machine and is unique for every design and is a constant value.
[016] In this invention in general, the voltage generated by the particular machine when rotated at a set rpm, is measured. The voltage generated is then compared to a pre-set value in the controller and based on this the traction motor is diagnosed for its parameters like air gap, magnet flux density, coil resistance and its deterioration. Based on the diagnostic data obtained the same can be transmitted to any other device and same can be displayed in plurality of ways.
[017] Figure 1 illustrates the method steps involves in a method 100 for diagnosing the traction motor of the hybrid type vehicle. As illustrated in the Figure 1, at step 1A, the engine is started by the user and the vehicle is run in an engine only mode. In this manner, the diagnosis of the traction motor of the hybrid type vehicle is initiated. At step 1B, a speed of the vehicle is measured. In that, the speed of the vehicle refers to the RPM of the engine. As a function of the speed of the vehicle, the volage generated by the back emf generated in the traction motor is measured. Resultantly, the back emf in the traction motor is calculated. In an embodiment of the invention, the back emf generated by the traction motor is measured using a dedicated Voltage Divider Circuit.
[018] At step 1C, the back emf generated in the traction motor is compared with a pre-determined value of back emf. This function is performed in the microcontrollers of the power controller. If the back emf generated in the traction motor is within a predetermined variance of the predetermined back emf value, this reflects that there is no deterioration in the traction motor and the method 100 moves to step 1CC, and the traction motor diagnosis is concluded with no deterioration detected in the traction motor. Conversely, if the back emf generated in the traction motor is not within a predetermined variance of the predetermined back emf value, this reflects a possibility of deterioration in the traction motor, and the requirement of further diagnosis to be carried out, and the method 100 moves to step 1D.
[019] At step 1D, the payload on the vehicle is detected. In that, the payload refers to the additional weight of the vehicle along with components, if any over and above the dry weight of the vehicle. At step 1E, whether the payload on the vehicle is zero, is detected. If the payload on the vehicle is detected to be zero, the method 100 moves to step 1EE and the diagnosis is terminated. If the payload is detected to not be zero, the method 100 moves to step 1F.
[020] At step 1F, the current in the traction motor is measured. Under normal running conditions with no deterioration in the traction motor, the traction motor will consume a specific value current for a specific value of the payload. However, if the payload not equal to zero and there has been some deterioration in the traction motor, the traction motor will consume more current than the earlier specific value of the current for the same amount of payload. Thereafter the method 100 moves to step 1G.
[021] At step 1G, the measure current in the traction motor is compared against a pre-set value of no load current. If the measured current in the traction motor is less than the pre-set no load current value, the method 100 moves to step 1H, and the traction motor is diagnosed as having no faults. If the measured current in the traction motor is greater than the pre-set no load current value, the method 100 moves to step 1GG.
[022] At step 1GG, the quality of the back emf generated by the traction motor is determined, which thereby diagnoses the condition of the traction motor. To facilitate this, in an embodiment, a Fast Fourier Transform is employed to determine the quality of the back emf. Any minute change in the air gap or change in magnetic field in the traction motor is detected by the analysis through the Fast Fourier Transform. The Fast Fourier Transform analyses the variation in the back emf generated in the traction motor against pre-stored data, and generates a fault code which is then communicated to the user via a communication device such as dashboard or a mobile application. Though the Fast Fourier Transform, loss in the magnetic field or any variation in the air gap caused by chipping of the magnets can be detected.
[023] In an embodiment, the method 100 is capable of operating in conjunction with other failure mode detection systems such as hall sensor errors, loss of power, or partial loss of power, which can then be highlighted as “Motor Malfunction” on the dashboard or the mobile application.
[024] Advantageously, the present invention provides a method which is capable of detecting any deformation in the traction motor. In most cases, the deformation in the traction motor can be detected prior to occurrence of any fault resulting from the deformation, thereby providing, in essence a prognosis of the traction motor.
[025] Further, for the implementation of the method, no additional hall sensors are required thereby bringing down the cost and complexity associated with traction motor diagnosis.
[026] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.