Starter generator control unit and starter generator system

Abstract

According to one aspect, a starter generator control unit can include a comparator, a pulse width modulation (PWM) duty cycle generator, a randomizer, and a sequencer. The comparator can receive a current reading from a current sensor and a target current from a target current lookup table and generate an output comparator signal indicating an increase or decrease in the current value of the pulse width modulation (PWM) duty cycle. The PWM duty cycle generator can receive the signal from the comparator and generate an output PWM signal. The randomizer can generate a random time-varying update signal. The PWM duty cycle generator can receive the random time-varying update signal, which can control a period time associated with the PWM duty cycle generator. The sequencer can receive the output PWM signal and generate gate signals for controlling an inverter based on the output PWM signal.

Description

Background Technology

[0001] Highly efficient and powerful electric starter generators (SGs) are generally desirable. Different types of SGs exist, such as brushed SGs and brushless SGs. Brushless SGs can be controlled using brushless motor control algorithms. Typically, an SG controller controls the SG by using relative rotor and / or stator position information and phase current and / or voltage information to control the inverter's pulse width modulation (PWM). Given a given DC power supply voltage to the inverter, the motor torque is controlled by controlling the output voltage lead angle and by controlling the current.

[0002] The phase current adjustment based on current feedback is performed at given constant intervals. During engine start-up, the SG speed changes from 0 rpm to the start-off speed rpm or a threshold rpm. This effectively creates a frequency sweep applied to the SG, transmission, and engine systems. However, the interaction between the constant feedback control update frequency, engine acceleration, and system mechanical resonance can potentially lead to unstable SG operation, with a high probability of this. Resonance can occur when the control loop adjusts the inverter PWM at regular, equal intervals during engine acceleration. This resonant behavior may cause unsuccessful engine start-up, resulting in start-stop, or may cause shearing of the generator shaft.

[0003] Furthermore, typical approaches often require enhanced software control algorithms that actively adjust control parameters (i.e., current and lead angle) to avoid resonant behavior. Another drawback of this approach is the associated complexity and software dependency. Summary of the Invention

[0004] According to one aspect, the starter-generator control unit may include: a comparator, a pulse width modulation (PWM) duty cycle generator, a randomizer, and a sequencer. The comparator may receive a current reading from a current sensor and a target current from a target current lookup table, and generate an output comparator signal indicating an increase or decrease in the current value of the PWM duty cycle based on the comparison between the current reading and the target current. The PWM duty cycle generator may receive the signal from the comparator and generate an output PWM signal. The randomizer may generate a random time-varying update signal. The PWM duty cycle generator may receive the random time-varying update signal, and the random time-varying update signal may control the cycle time associated with the PWM duty cycle generator. The sequencer may receive the output PWM signal and generate a gate control signal for controlling the inverter based on the output PWM signal.

[0005] The starter generator control unit may include a clock that drives the randomizer. This clock may be a pseudo-random clock. A sequencer may receive the position angle associated with the starter generator driven by the inverter and generate a gate control signal for controlling the inverter based on that position angle. The starter generator control unit may receive the rotational speed associated with the starter generator driven by the inverter. A target current from a target current lookup table may be determined by the starter generator control unit based on the rotational speed associated with the starter generator driven by the inverter. The starter generator may include a resolver that determines the rotational speed. The rotational speed may be the time derivative of the position angle associated with the starter generator. The inverter may be associated with N phases. The output comparator signal may be associated with incrementing or decrementing.

[0006] According to one aspect, a system for randomized current feedback control of a starter generator control unit may include a comparator, a pulse width modulation (PWM) duty cycle generator, a randomizer, an inverter, and a sequencer. The comparator may receive a current reading from a current sensor and a target current from a target current lookup table, and generate an output comparator signal indicating an increase or decrease in the current value of the PWM duty cycle based on the comparison between the current reading and the target current. The PWM duty cycle generator may receive the signal from the comparator and generate an output PWM signal. The randomizer may generate a random time-varying update signal. The PWM duty cycle generator may receive the random time-varying update signal, and the random time-varying update signal may control the period time associated with the PWM duty cycle generator. The sequencer may receive the output PWM signal and generate a gate control signal for controlling the inverter based on the output PWM signal.

[0007] A system for randomized current feedback control of a starter-generator control unit may include a clock driving the randomizer. This clock may be a pseudo-random clock. A sequencer may receive the position angle associated with the starter-generator driven by the inverter and generate a gate control signal for controlling the inverter based on that position angle. The starter-generator control unit may receive the rotational speed associated with the starter-generator driven by the inverter. A target current from a target current lookup table may be determined by the starter-generator control unit based on the rotational speed associated with the starter-generator driven by the inverter. The starter-generator may include a resolver for determining the rotational speed. The rotational speed may be the time derivative of the position angle associated with the starter-generator. The inverter may be associated with N phases.

[0008] A method for randomized current feedback control of a starter-generator control unit may include: receiving a current reading from a current sensor and a target current from a target current lookup table using a comparator, and generating an output comparator signal indicating an increase or decrease in a current value based on a comparison between the current reading and the target current; receiving the signal from the comparator using a PWM duty cycle generator and generating an output PWM signal; generating a randomized time-varying update signal using a randomizer, and receiving the randomized time-varying update signal using the PWM duty cycle generator. The randomized time-varying update signal can control the cycle time associated with the PWM duty cycle generator. The method may also include receiving the output PWM signal using a sequencer and generating a gate control signal for controlling an inverter based on the output PWM signal. Attached Figure Description

[0009] Figure 1 This is an exemplary component diagram of a system for randomized current feedback control of a starter generator control unit (SGCU) according to one aspect.

[0010] Figure 2 This is an exemplary flowchart of a method for randomized current feedback control of a starter generator control unit (SGCU) according to one aspect. Detailed Implementation

[0011] Brushless motor control algorithms can be used to control brushless starter generators (SGs). When the brushless SG operates in starter mode, the brushless motor control algorithm can be optimized to effectively drive the brushless generator.

[0012] Brushless starter generators (SGs) can typically be optimized for operation in generator mode, as they generally operate in this mode for more than 90% of the time. According to one aspect, the starter generator control unit (SGCU) can be designed to provide high starting torque by implementing an SG controller that uses randomized current feedback to control the SG. In other words, instead of using regular, equal pulse width modulation (PWM) adjustment intervals, the systems and techniques described herein implement irregular adjustment intervals, which can be governed by a pseudo-random clock implemented in hardware. In this way, resonant behavior of the starting system can be mitigated, thereby improving the reliability of both the engine and the SG.

[0013] Figure 1This is an exemplary component diagram of a system 100 for randomized current feedback control of a starter generator control unit (SGCU) according to one aspect. The system 100 for randomized current feedback control of the SGCU can control a brushless SG during engine starting mode. The system 100 for randomized current feedback control of the SGCU may include a controller 102. The controller 102 may include a comparator 104, a pulse width modulation (PWM) duty cycle generator 106, a randomizer 108, a sequencer 112, and a clock 114.

[0014] exist Figure 1 As can be seen, DC power supply 152 provides DC power to inverter 156, which drives a multiphase starter generator (SG) 158 that can be associated with N phases. System 100 for randomized current feedback control of the SGCU may include an SGCU or controller 102 that controls the inverter 156. For example, system 100 for randomized current feedback control of the SGCU can control the brushless SG 158 during engine start-up mode by controlling the current supplied from DC power supply 152 to inverter 156.

[0015] Current sensor 154 can measure the current associated with DC power supply 152 and provide this measurement as an input to controller 102. Furthermore, multiphase SG 158 can provide position angle and rotational speed (e.g., time derivative of position angle) as input to controller 102 via resolver 162 of the multiphase SG. Rotational speed can be the time derivative of the position angle associated with the SG. SG 158 can include resolver 162 that determines the position angle and / or rotational speed. In other words, when SG 158 rotates, resolver 162 with the SG mounted can provide position angle and time derivative of position angle or rotational speed to controller 102. SGCU can receive rotational speed 156 associated with SG 158 driven by inverter.

[0016] like Figure 1 As seen, a closed-loop control system can be used to implement DC source current feedback control. The position angle can be used to control the sequencer 112, and thus control the sequencing of the inverter gate drive signals for the inverter transistors.

[0017] Using the position angle provided by the resolver 162 of the multiphase SG, the controller 102 can determine the target current via a lookup table, which can be stored in the memory drive 120 of the controller 102. The lookup table can indicate the target current at a given rotational speed of the multiphase SG. In this way, the controller 102 can determine the target current value based on the input of the position angle and / or rotational speed, as well as the lookup table. In other words, the rotational speed can be used to address the target current lookup table stored in the memory or memory drive 120 of the controller 102 and the associated calculations performed by the processor of the controller 102. According to one aspect, the target current value varies with the rotational speed within the lookup table. In this way, the controller 102 can regulate the source current in a manner that controls the inverter PWM so that the instantaneous power supply current value is equal to the target current value from the lookup table. The target current from the target current lookup table can be determined by the SGCU based on the rotational speed associated with the SG 158 driven by the inverter 156.

[0018] Comparator 104 within controller 102 can compare a target current value with the current associated with the DC power supply 152 provided by the DC source current sensor output. Comparator 104 can determine whether to increase or decrease the current value of the PWM duty cycle. Comparator 104 can determine whether to increase or decrease the current value of the PWM duty cycle based on the need to increase or decrease the inverter input current. For example, the PWM duty cycle can be incremented or decremented by the same amount each time a current correction is determined. Comparator 104 can receive a current reading from current sensor 154 and a target current from a target current lookup table (e.g., which may be stored in memory driver 120 or received by controller 102, depending on other aspects) and generate an output comparator signal indicating an increase or decrease in the current value of the PWM duty cycle based on the comparison between the current reading and the target current.

[0019] An incrementing or decrementing control loop can be run until the PWM adjustment results in a match between the controlled variable (e.g., the target current from the lookup table) and the measured feedback value (e.g., the current measured from the current sensor 154).

[0020] The randomizer 108 within controller 102 can generate a random time-varying update signal (based on clock 114), which can be fed to PWM duty cycle generator 106 to indicate when to update the pulse width using new adjustments from comparator 104. Controller 102 for SGCU randomized current feedback control may include clock 114 driving randomizer 108. Clock 114 may be a pseudo-random clock.

[0021] The PWM duty cycle generator 106 can receive a random time-varying update signal, which can control the period time associated with the PWM duty cycle generator 106. The PWM duty cycle generator 106 can receive a signal from the comparator 104 and generate an output PWM signal. The output of the PWM duty cycle generator 106 provides the generated pulse width to the sequencer 112, which in turn changes the amount of current drawn from the DC source. The use of randomized feedback correction mitigates resonance in the starter generator or SG 158 during speed acceleration and reduces unwanted torque fluctuations.

[0022] The sequencer 112 can receive the output PWM signal and generate a gate control signal for controlling the inverter 156 based on the output PWM signal. The sequencer 112 can also receive the position angle associated with the SG 158 driven by the inverter 156 and generate a gate control signal for controlling the inverter 156 based on the position angle.

[0023] According to one aspect, the randomizer 108 can change the frequency associated with the update frequency of the battery current value. For example, a control pulse can be provided that enables the updating of the battery current value to be changed. A battery current feedback signal (e.g., battery_current_feedback_logic) can be implemented to control the field-programmable gate array (FPGA) design of the system 100 used for randomized current feedback control of the SGCU. The battery current feedback signal can be provided such that if the current exceeds the midpoint, it decreases, and if the current falls below the midpoint, it increases by an increment (e.g., + / - 1 increment or unit per sampling period).

[0024] Examples of such variations could include: waiting 1ms until the next update, waiting 2ms until the next update, waiting 3ms until the next update, waiting 4ms until the next update, etc. The randomizer 108 can control the periodicity of the control pulses periodically. This can be achieved, for example, using a pseudo-random number generator within the randomizer 108. The randomizer 108 can include a state machine controlling the sequencer 112. For example, the output signal of the pseudo-random number generator (e.g., prng_to_start_batt_curr_fb_correction) can be utilized by the firmware module sm_battery_current_feedback, which can be a state machine acting as the controller 102 of the sequencer 112 for the battery current feedback algorithm.

[0025] In this way, mechanical and / or electrical resonances during engine start-up or SG 158 speed acceleration caused by control loop adjustments can be mitigated or avoided. Starter torque fluctuations can be significantly reduced, thereby improving the reliability of the system 100 used for randomized current feedback control of the SGCU.

[0026] Figure 2 This is an exemplary flowchart of a method 200 for randomized current feedback control of a starter generator control unit, according to one aspect. The method 200 for randomized current feedback control of a starter generator control unit may include: receiving 202 a current reading from a current sensor and a target current from a target current lookup table using a comparator, and generating 204 an output comparator signal indicating an increase or decrease in the current value of a pulse width modulation (PWM) duty cycle based on a comparison between the current reading and the target current; receiving the signal from the comparator using a PWM duty cycle generator 106 and generating 206 an output PWM signal; generating 208 a randomized time-varying update signal using a randomizer, and receiving the randomized time-varying update signal using the PWM duty cycle generator 106. The randomized time-varying update signal can control the period time associated with the PWM duty cycle generator 106. The method 200 may include receiving the output PWM signal using a sequencer and generating 210 a gate control signal for controlling an inverter based on the output PWM signal.

[0027] Similarly, the implementation of method 200 for randomized current feedback control of SGCU can mitigate mechanical and / or electrical resonant coupling during engine acceleration by using a random time base during start-up mode to apply feedback loop correction to the starter generator or SG controller.

[0028] It should be understood that the various above-mentioned and other features and functions, or their alternatives or variations, can be expected to be combined into many other different systems or applications. Furthermore, those skilled in the art can subsequently make various substitutions, modifications, variations, or improvements therein that are not currently foreseen or anticipated, and which are also intended to be covered by the following claims.

Claims

1. A starter-generator control unit, comprising: The DC power supply is configured to provide DC current; Inverter, coupled to the DC power supply; A current sensor, coupled between the inverter and the DC power supply, is configured to generate a current reading associated with the DC power supply. A comparator configured to receive the current reading from the current sensor and a target current from a target current lookup table, and further configured to generate an output comparator signal indicating an increase or decrease in the current value of a pulse width modulation (PWM) duty cycle based on a comparison between the current reading and the target current. A PWM duty cycle generator, the PWM duty cycle generator being configured to receive the output comparator signal from the comparator and generate an output PWM signal; A randomizer is configured to generate a random time-varying update signal, wherein the PWM duty cycle generator is further configured to receive the random time-varying update signal, the random time-varying update signal being configured to control the period time associated with the PWM duty cycle generator, and the randomizer being configured to change the frequency associated with updating the battery current value, wherein updating the battery current value includes: decreasing the DC current at the inverter if the battery current value exceeds a midpoint, or increasing the DC current at the inverter if the battery current value is below the midpoint; A controller configured to receive the rotational speed associated with the starter generator driven by the inverter; A rotary transformer configured to determine the rotational speed, the rotational speed being the time derivative of the position angle associated with the starter generator; and A sequencer configured to receive the output PWM signal and the rotational speed associated with the starter generator, and configured to generate a gate control signal for controlling the inverter based on the output PWM signal, wherein the amount of DC current drawn from the DC power supply to the inverter is changed based on the gate control signal, and wherein the random time-varying update signal is configured to attenuate the resonant frequency of the starter generator during acceleration.

2. The starter-generator control unit according to claim 1, comprising a clock that drives the randomizer.

3. The starter-generator control unit according to claim 2, wherein the clock is a pseudo-random clock.

4. The starter-generator control unit of claim 1, wherein the sequencer is configured to receive a position angle associated with the starter-generator driven by the inverter, and generate a gate control signal for controlling the inverter based on the position angle.

5. The starter generator control unit of claim 1, wherein the starter generator control unit is configured to receive the rotational speed associated with the starter generator driven by the inverter.

6. The starter-generator control unit of claim 5, wherein the target current from the target current lookup table is determined by the starter-generator control unit based on the rotational speed associated with the starter-generator driven by the inverter.

7. The starter generator control unit of claim 5, wherein the starter generator includes a rotary transformer for determining the rotational speed.

8. The starter-generator control unit of claim 1, wherein the inverter is associated with N phases.

9. The starter generator control unit of claim 1, wherein the output comparator signal is associated with incrementing or decrementing.

10. A system for randomized current feedback control of a starter-generator control unit, comprising: Starter generator; The DC power supply is configured to provide DC current; Inverter, coupled to the DC power supply; A current sensor, coupled between the inverter and the DC power supply, is configured to generate a current reading associated with the DC power supply. A comparator configured to receive a current reading from the current sensor and a target current from a target current lookup table, and to generate an output comparator signal indicating an increase or decrease in the current value of a pulse width modulation (PWM) duty cycle based on a comparison between the current reading and the target current. A PWM duty cycle generator, the PWM duty cycle generator being configured to receive the output comparator signal from the comparator and generate an output PWM signal; A randomizer is configured to generate a random time-varying update signal, wherein a PWM duty cycle generator is configured to receive the random time-varying update signal, the random time-varying update signal controlling a period time associated with the PWM duty cycle generator, and the randomizer is configured to change a frequency associated with updating a battery current value, wherein updating the battery current value includes: decreasing the DC current at the inverter if the battery current value exceeds a midpoint, or increasing the DC current at the inverter if the battery current value is below the midpoint; A controller configured to receive the rotational speed associated with the starter generator driven by the inverter; A rotary transformer configured to determine the rotational speed, the rotational speed being the time derivative of the position angle associated with the starter generator; and A sequencer configured to receive the output PWM signal and the rotational speed of the inverter associated with the starter generator, and configured to generate a gate control signal for controlling the inverter based on the output PWM signal, wherein the amount of DC current drawn from the DC power supply to the inverter is changed based on the gate control signal, and wherein the random time-varying update signal is configured to attenuate the resonant frequency of the starter generator during acceleration.

11. The system for randomized current feedback control of a starter generator control unit according to claim 10, comprising a clock driving the randomizer.

12. The system for randomized current feedback control of a starter-generator control unit according to claim 11, wherein the clock is a pseudo-random clock.

13. The system for randomized current feedback control of a starter generator control unit according to claim 10, wherein the sequencer receives a position angle associated with a starter generator driven by the inverter and generates a gate control signal for controlling the inverter based on the position angle.

14. The system for randomized current feedback control of a starter-generator control unit according to claim 10, wherein the target current from the target current lookup table is determined by the starter-generator control unit based on the rotational speed associated with the starter-generator driven by the inverter.

15. The system for randomized current feedback control of a starter generator control unit according to claim 10, wherein the inverter is associated with N phases.

16. A method for randomized current feedback control of a starter-generator control unit, comprising: The comparator receives current readings from a current sensor coupled between the DC power supply and the inverter and a target current from a target current lookup table, and generates an output comparator signal that indicates an increase or decrease in the current value of the pulse width modulation (PWM) duty cycle based on the comparison between the current readings and the target current. A PWM duty cycle generator is used to receive signals from the comparator and generate an output PWM signal. A random time-varying update signal is generated using a randomizer, wherein the PWM duty cycle generator receives the random time-varying update signal, and the random time-varying update signal controls the period time associated with the PWM duty cycle generator; The randomizer changes the frequency associated with updating the battery current value, wherein updating the battery current value includes: reducing the DC current at the inverter if the battery current value exceeds the midpoint, or increasing the DC current at the inverter if the battery current value is below the midpoint. The rotational speed is determined using a rotary transformer; the rotational speed is the time derivative of the position angle associated with the starter generator. The sequencer receives the output PWM signal and the rotational speed associated with the starter generator driven by the inverter, and generates a gate control signal for controlling the inverter based on the output PWM signal, wherein the amount of DC current drawn from the DC power supply to the inverter is changed based on the gate control signal, and wherein the random time-varying update signal attenuates the resonant frequency of the starter generator.

17. The method of claim 16, further comprising: The randomizer controls the control pulses to update the frequency associated with the battery current value.

18. The method of claim 17, further comprising: A battery current feedback signal is received at the randomizer, wherein the frequency is at least partially based on the battery current feedback signal.

19. The method of claim 18, further comprising: Determine whether the battery current feedback signal is above or below the midpoint, wherein: If the battery current feedback signal is above the midpoint, the current supplied to the battery will decrease in increments; or If the battery current feedback signal is below the midpoint, the current supplied to the battery will be increased by the increment.

20. The method of claim 19, wherein the randomizer controls the control pulse to update a first battery current value during a first cycle to a second battery current value during a second cycle.

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