Field of the invention:
[0001] The present invention relates to controller to diagnose failure of a crankshaft position sensor in a vehicle and a method thereof.
Background of the invention:
[0002] According to a prior art US2002092344 a diagnostic method for a shaft sensor in a reciprocating internal combustion engine is disclosed. An improved method of diagnosing shaft sensor failure in a reciprocating internal combustion engine verifies engine rotation by sensor information responsive to dynamic variation in engine air intake that occurs during engine rotation. Failure of the shaft sensor is diagnosed when the dynamic variation in engine air intake is detected in the absence of a shaft sensor signal. The sensor information used to detect the dynamic variation in intake air may be obtained from either a mass air flow sensor disposed in a throttle passage of the engine, or from a pressure sensor disposed in an intake manifold of the engine, and virtually all current engine control systems utilize at least one of these sensors. The dynamic variation is detected by recognizing rising and falling segments of the signal waveform, by comparing the relative manifold pressure to predetermined maximum and minimum values, or by using a derivative of the signal waveform to recognize its inflection points.
[0003] An operational check for a crankshaft position sensor is a mandatory legal requirement as a part of future regulations as per On Board Diagnostics (OBD). In the current available system, diagnosis of the crankshaft position sensor is done by comparing position signal of the crankshaft sensor against Manifold Absolute Pressure (MAP) sensor (pulsation caused during intake stroke) or against drop in a battery voltage, during engagement of starter motor. There is a need for a new solution which diagnoses without using a MAP sensor and/ or the battery voltage.
Brief description of the accompanying drawings:
[0004] An embodiment of the disclosure is described with reference to the following accompanying drawing,

[0005] Fig. 1 illustrates a controller to diagnose a fault in a crankshaft position
sensor, according to an embodiment of the present invention;
[0006] Fig. 2 illustrates a method for diagnosing a fault in the crankshaft position
sensor, according to the present invention, and
[0007] Fig. 3 illustrates the controller to diagnose a fault in a crankshaft position
sensor using only a position signal, according to an embodiment of the present
invention.
Detailed description of the embodiments:
[0008] Fig. 1 illustrates a controller to diagnose a failure in a crankshaft position sensor, according to an embodiment of the present invention. The controller 102 is an Engine Control Unit (ECU) of a vehicle or a dedicated control unit in communication with the ECU of the vehicle. The controller 102 is adapted to detect any one of a first signal 110 and a second signal 120. The first signal 110 corresponds to a voltage generated by an electric machine 106 coupled to an engine. The second signal 120 corresponds to a status of a drivetrain of the vehicle. The controller 102 further detects a position signal 130 from the crankshaft position sensor 104, upon detection of any one of the first signal 110 and the second signal 120. The controller 102 diagnoses fault in the crankshaft position sensor 104 based on a status of the position signal 130. The status of the position signal 130 is selected from “absent” and “abnormal”. The Fig. 1 illustrates a typical crankshaft position sensor 104 held in proximity of a trigger wheel or tooth wheel 108. The crankshaft position sensor 104 is electrically connected to the controller 102. Further, a graph 116 of voltage of alternator versus time is provided for the electric machine 106. The X-axis 112 corresponds to time in suitable unit such as milliseconds (ms) and the Y-axis 114 corresponds to voltage of the alternator electric machine 106. The first signal 110 is shown as a representation and must not be understood in limiting manner. The position signal 130 from the crankshaft position sensor 104 is also shown. The position signal 130 is sinusoidal in nature. However, a square wave signal or other types of signal are also possible and is not limited thereto.

[0009] In accordance to an embodiment of the present invention, the vehicle is devoid/without a MAP sensor. The vehicle is also without a starter motor and a respective battery. The controller 102 is solely powered by the electric machine 106 through a power supply circuit. The power supply circuit is without a filter capacitor. The accessories of the vehicle may be powered by a separate battery or by directly by the electric machine 106. When the engine is cranked by a kick-start lever, the electric machine 106 starts generating electric energy and the first signal 110 is obtained. The electric energy powers the controller 102. The controller 102 switches ON or wakes up. There is a delay in operation of the controller 102. After the controller 102 is ON, the controller 102 compares the first signal 110 with a threshold value to detect a predetermined gradient of the first signal 110. Once the gradient is confirmed, the controller 102 starts detecting the presence or status of the position signal 130 from the crankshaft position sensor 104. If the position signal 130 is detected to be absent, the controller 102 diagnoses the crankshaft position sensor 104 to be faulty.
[0010] In accordance to another embodiment of the present invention, a capacitor is provided in a power supply circuit for the voltage generated by the electric machine 106. The capacitor holds the charge for a duration of time depending on the power consumption of the controller 102 and the size of the capacitor. After this time if the engine is OFF then the controller 102 shuts down as there is no power supply to keep the engine running. However, even if after a time delay the controller 102 is still ON and the position signal 130 from the crankshaft position sensor 104 is absent, then the crankshaft position sensor 104 is diagnosed as faulty.
[0011] In accordance to an embodiment of the present invention, the vehicle is provided with a MAP sensor, but without the starter motor and the respective battery. However, the MAP sensor is faulty or provides an erroneous signal or is disconnected. The controller 102 is solely powered by the electric machine 106. When the engine is cranked by kick-start lever, the electric machine 106 starts generating electric energy and the first signal 110 is obtained. The electric energy

powers the controller 102. The controller 102 switches ON or wakes up. After the controller 102 is ON, the controller 102 compares the first signal 110 with a threshold value to detect a predetermined gradient of the first signal 110. Once the gradient is confirmed, the controller 102 starts detecting the presence of the position signal 130 from the crankshaft position sensor 104. If the position signal 130 is detected to be absent, the controller 102 diagnoses the crankshaft position sensor 104 to be faulty. Thus, the controller 102 is able to diagnose failure of the crankshaft position sensor 104 when the MAP sensor becomes faulty or is unavailable.
[0012] In accordance to another embodiment of the present invention, the vehicle is provided with the MAP sensor and the starter motor along with respective battery, and all are functional. The controller 102 is powered either by the battery and/or the electric machine 106. If the battery powers the controller 102, then the delay of switching ON the controller 102 is avoided. The controller 102 is enabled to diagnose the failure of the crankshaft position sensor 104 without using the signal from MAP sensor and the battery voltage, i.e. the controller 102 uses the first signal 110. To elaborate further, the vehicle is started using the kick-start lever even though there is a starter motor. The controller 102 powered by the battery checks the first signal 110, which is the output by the electric machine 106 during starting. The controller 102 subsequently checks the presence of the second signal 120 after detecting the first signal to determine whether the crankshaft position sensor 104 is faulty or not.
[0013] In accordance to another embodiment of the present invention, the vehicle is provided without the MAP sensor, but with the starter motor along with respective battery. During the normal working of the vehicle, consider the battery is drained or dead or is disconnected. In these conditions, the controller 102 is independent of the battery voltage to diagnose a failure of the crankshaft position sensor 104, by making use of only the first signal 110 generated by the electric machine 106.

[0014] The electric machine 106 is at least one of an Integrated Starter Generator (ISG), an alternator and a magneto.
[0015] In accordance to an embodiment of the present invention, the controller 102 detects the presence of the position signal 130 with the first signal 110 of the electric machine 106, irrespective of the state of the battery or availability or connection of the battery.
[0016] In yet another embodiment of the present invention, the controller 102 detects the presence of the position signal 130 with the first signal 110 of the electric machine 106 when a signal from a Manifold Absolute Pressure (MAP) sensor is any one of erroneous and unavailable.
[0017] In accordance to another embodiment of the present invention, the controller 102 is adapted to perform the respective steps only when the MAP sensor and/or the battery for the starter motor are either not available or are dead or faulty or disconnected. In another embodiment, the present invention is implemented to a battery less vehicle.
[0018] In accordance to another embodiment of the present invention, the second signal 120 is detected based on a non-zero speed from a vehicle speed sensor, a clutch engaged signal and a gear engaged signal. The controller 102 then checks the status of the crankshaft position sensor 104. If the crankshaft position sensor 104 is abnormal such as not to expected value or absent then, the controller 102 diagnoses a fault. Here, the controller 102 is powered by either the electric machine 106 and/or the battery.
[0019] The vehicle is any one selected from a group comprising a two-wheeler such as motorcycles, three-wheelers, four-wheelers and the like. Specifically, the present invention is implemented but not limited thereto, for racing motorcycles, off-road

racing motorcycles etc., where the battery is removed in view of reducing the weight of the bikes. Further, the MAP sensor is also not present.
[0020] Fig. 2 illustrates a method for diagnosing a fault in the crankshaft position sensor, according to the present invention. The method comprising the steps of a step 202 comprising detecting any one of the first signal 110 and the second signal 120. The first signal 110 corresponds to the voltage generated by the electric machine 106 coupled to the engine. The second signal 120 corresponds to the status of the drivetrain. A step 204 comprises detecting the position signal 130 from the crankshaft position sensor 104, upon detection of any one of the first signal 110 and the second signal 120. A step 206 comprises diagnosing a fault in the crankshaft position sensor 104 based on the status of the position signal 130. The status comprises the position signal 130 to be any one of absent and abnormal. A gradient of the first signal 110 is compared against a threshold value, before detecting presence of the position signal 130. The electric machine 106 is at least one of an Integrated Starter Generator (ISG), an alternator and a magneto. The engine is cranked by any one of a starter motor and a Kick-start lever.
[0021] The method comprising the second signal 120 is explained below. The second signal 120 is detected based on a non-zero speed from a vehicle speed sensor, a clutch engaged signal and a gear engaged signal. If the crankshaft position sensor 104 is detected to be abnormal, i.e. either not to the expected value of absent, then method diagnoses a fault in the crankshaft position sensor 104.
[0022] The method is applicable for a battery less vehicle or the vehicle where the state of the battery is at least one of a dead and disconnected. The method is also applicable if the battery is charged and connected.
[0023] Fig. 3 illustrates the controller to diagnose a fault in the crankshaft position sensor using only the position signal, according to an embodiment of the present invention. The controller 102 is adapted to measure an engine speed from the

position signal 130 detected by the crankshaft position sensor 104. The controller 102 compares the engine speed with a reference signal, and diagnoses a fault in the crankshaft position sensor 104 based on the result of the comparison. The reference value is stored in the memory element 302 of the controller 102. In one case, the reference signal is a speed pattern during engine shut down. If the reduction in the engine speed during engine shutdown does not match with the reference signal, such as abruptly going to zero, then the controller 102 diagnoses the crankshaft position sensor 104 to be faulty.
[0024] In another case, the reference signal represents minimum and maximum possible engine speed. If the crankshaft position sensor 104 senses a signal different or outside the limits defined by the reference signal, then the controller 102 diagnoses the crankshaft position sensor 104 to be faulty.
[0025] According to the embodiment described in the Fig. 2, a method for diagnosing fault in the crankshaft position sensor 104 in the vehicle is provided. The method comprising the steps of a first step comprising measuring the engine speed from the position signal 130 detected by the crankshaft position sensor 104. A second step comprising comparing the engine speed with the reference signal. A third step comprising diagnosing fault in the crankshaft position sensor 104 upon failure of the comparison. The reference signal is a speed pattern during engine shut down. Alternatively, the reference signal represents minimum and maximum possible engine speed.
[0026] According to an embodiment of the present invention, the controller 102 is provided for diagnosing a crankshaft position sensor 104 for a battery less and dead battery vehicles. The controller 102 is able to detect the failure of the crankshaft position sensor 104 both during starting and during run time. Any abrupt failure of the vehicle such as sudden engine stall condition, etc., is avoided reliably by detecting the failure of the crankshaft position sensor 104 and followed by possible

corrective action such as switching the vehicle to a “safe mode” or “limp home mode”.
[0027] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.

We claim:
1. A controller (102) to diagnose a fault in a crankshaft position sensor (104)
of a vehicle, said controller (102) adapted to:
detect any one of a first signal (110) and a second signal (120), said
first signal (110) corresponds to a voltage generated by an electric
machine (106) coupled to an engine, and said second signal (120)
corresponds to a status of a drivetrain;
detect a position signal (130) from said crankshaft position sensor
(104), upon detection of any one of said first signal (110) and said
second signal (120), and
diagnose fault in said crankshaft position sensor (104) based on a
status of said position signal (130).
2. The controller (102) as claimed in claim 1, wherein a gradient of said first signal (110) is compared against a threshold value.
3. The controller (102) as claimed in claim 1, wherein said electric machine (106) is at least one of an Integrated Starter Generator (ISG), an alternator and a magneto.
4. The controller (102) as claimed in claim 1, wherein a battery of said vehicle is in at least one of a state of dead and disconnected.
5. The controller (102) as claimed in claim 1, wherein said vehicle is a battery less vehicle.
6. The controller (102) as claimed in claim 1, wherein said status of drivetrain is detected based on a non-zero speed from a vehicle speed sensor, a clutch engaged signal and a gear engaged signal.

7. A method for diagnosing a fault in a crankshaft position sensor (104) in a
vehicle, said method comprising the steps of:
detecting any one of a first signal (110) and a second signal (120),
said first signal (110) corresponds to a voltage generated by an
electric machine (106) coupled to an engine, and said second signal
(120) corresponds to a status of a drivetrain;
detecting a position signal (130) from said crankshaft position sensor
(104), upon detection of any one of said first signal (110) and said
second signal (120), and
diagnosing fault in said crankshaft position sensor (104) based on a
status of said position signal (130).
8. The method as claimed in claim 7, wherein a gradient of said first signal (110) is compared against a threshold value.
9. The method as claimed in claim 7, wherein said electric machine (106) is at least one of an Integrated Starter Generator (ISG), an alternator and a magneto.
10. The method as claimed in claim 7, wherein a battery of said vehicle is in at least one of a state of dead and disconnected.
11. The method as claimed in claim 7, wherein said vehicle is a battery less vehicle.
12. The method as claimed in claim 7, wherein said status of drivetrain is detected based on a non-zero speed from a vehicle speed sensor, a clutch engaged signal and a gear engaged signal.