Motor Control - Revision history

Jsimon38: /* Inverter Setup */

2024-12-25T09:16:16Z

Inverter Setup

Jsimon38: /* Inverter Setup */

2024-12-25T09:15:40Z

Inverter Setup

Jsimon38 at 08:59, 25 December 2024

2024-12-25T08:59:33Z

Jsimon38: /* Field Oriented Control for Synchronous Machines */

2024-12-25T08:56:30Z

Field Oriented Control for Synchronous Machines

Jsimon38 at 08:53, 25 December 2024

2024-12-25T08:53:36Z

Jsimon38 at 00:47, 3 January 2024

2024-01-03T00:47:39Z

Etrain Troy: /* Torque Regulation */

2022-06-21T00:21:23Z

Torque Regulation

Etrain Troy: /* Current Regulation */

2022-06-21T00:15:19Z

Current Regulation

Etrain Troy: /* Field Oriented Control for Synchronous Machines */

2022-06-21T00:14:16Z

Field Oriented Control for Synchronous Machines

Etrain Troy: /* Resolvers & Encoders */

2022-06-21T00:08:57Z

Resolvers & Encoders

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 * <span>Phase current limit: sets the limit of the current in any of the motor's 3 phases. This is directly proportional to the torque that the motor produces. This is NOT the same as the battery current and can be 2-3x higher based on the Kv (voltage constant) of the motor windings.</span>
 * <span>PI loop gains: Changes the aggressiveness of the PI loops when there is an error between reference & measured DQ currents. These are typically preset by the controller manufacturer for specific motors and SHOULD NOT be changed unless there is an obvious issue with how the controller is commanding current</span>
-** <span>One way to tune these is to observe overshoot & drift in the commanded DQ currents: more overshoot indicates Kp may be too high while excessive drift means Ki should be increased</span>
+** <span>One way to tune these is to observe overshoot & drift in the commanded DQ currents: more overshoot indicates Kp may be too high while excessive drift means Ki may be too low</span>
 =Six-Step Control=

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 =Inverter Setup=
 While the theory behind FOC is important to understand, most teams should be focusing on getting their motor controller working with their motor. This means understanding what parameters can be changed in a typical motor controller and how that may affect the operation of your motor. Some common parameters include:
 =Six-Step Control=

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 Motor control is a complex field which requires knowledge of linear algebra, control theory, and an understanding of electric machines. However, the overarching goal of every style of motor control is this keyword (look it up): rotating magnetic field, or RMF. This page aims to break down various styles of motor control, but focuses on the primary modern method, Field-Oriented Control or FOC.
-=DC Brushed Motor Control=
+=Inverter Setup=
 =Six-Step Control=
 =Field Oriented Control for Synchronous Machines=

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 =Field Oriented Control for Synchronous Machines=
 Most FSAE-grade motor controllers use Field-Oriented Control. This decouples the torque and flux (magnetic field strength) control within the motor, which offers improved efficiency and dynamic performance of the motor & controller. To summarize, there are 7 main steps to FOC.
-) Measure phase currents and rotor position - done using 2 or 3 phase current sensors + encoder/resolver for rotor position
+# Measure phase currents and rotor position - done using 2 or 3 phase current sensors + encoder/resolver for rotor position
-) Clarke transform - linear transformation from the 3-phase stationary (abc) to 2-phase stationary (alpha/beta) of the currents in the stator windings
+# Clarke transform - linear transformation from the 3-phase stationary (abc) to 2-phase stationary (alpha/beta) of the currents in the stator windings
-) Park transform - linear transformation from the 2-phase stationary (alpha/beta) to 2-phase rotating frame (DQ) - this turns the 2-phase currents in the stator windings into 2-phase currents that the rotor sees as it rotates
+# Park transform - linear transformation from the 2-phase stationary (alpha/beta) to 2-phase rotating frame (DQ) - this turns the 2-phase currents in the stator windings into 2-phase currents that the rotor sees as it rotates
-- Here is the important part: the Q-axis of the rotor is what controls torque while the D-axis of the rotor controls the flux. Since we can request D and Q-axis currents independently now, we can control the torque and flux separately respectively.
+## Here is the important part: the Q-axis of the rotor is what controls torque while the D-axis of the rotor controls the flux. Since we can request D and Q-axis currents independently now, we can control the torque and flux separately respectively
-) PI control loops: set the D-axis and Q-axis currents of the rotor based on the error between reference values given by throttle position and measured values from the phase current & rotor position sensors
+# PI control loops: set the D-axis and Q-axis currents of the rotor based on the error between reference values given by throttle position and measured values from the phase current & rotor position sensors
-) Inverse-Park transform: going back from the 2-phase rotating (DQ) frame to the 2-phase stationary (alpha/beta) frame
+# Inverse-Park transform: going back from the 2-phase rotating (DQ) frame to the 2-phase stationary (alpha/beta) frame
-) Inverse-Clarke transform: going back from the 2-phase stationary (alpha/beta) to the 3-phase stationary (abc) frame
+# Inverse-Clarke transform: going back from the 2-phase stationary (alpha/beta) to the 3-phase stationary (abc) frame
-) SVPWM: space-vector pulse-width modulation: calculates the required PWM signals for the IGBT/MOSFET half-bridges to generate the correct 3x AC phase voltages which drive currents in each phase
+# SVPWM: space-vector pulse-width modulation: calculates the required PWM signals for the IGBT/MOSFET half-bridges to generate the correct 3x AC phase voltages which drive currents in each phase
 ==Transformations==
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 ====Calibration====
 ==Space Vector PWM==
 =Field Oriented Control for Asynchronous Machines=

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 [[Category:Electric Vehicle]]
 =DC Brushed Motor Control=
 =Six-Step Control=
 =Field Oriented Control for Synchronous Machines=
-Most fsae grade motor controllers use field oriented control. This is due to the improved efficiency and dynamic performance of the controller and motor controller. This control scheme relies on controller the DQ-axis currents by applying a DQ-axis voltage.
+Most FSAE-grade motor controllers use Field-Oriented Control. This decouples the torque and flux (magnetic field strength) control within the motor, which offers improved efficiency and dynamic performance of the motor & controller. To summarize, there are 7 main steps to FOC.
 ==Transformations==
 ===Clarke Transform===
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 There are a couple ways to calculation the required current to achieve a desired torque
 ===Zero D-Axis Current===
 ===Maximum Torque Per Amp (MTPA)===
-MPTA is a control strategy to obtain the greatest torque out of higher-reluctance motors per amp of current given. This is especially true for Interior Permanent Magnet (IPM) AC motors for which the rotor's magnets are buried in the rotor, rather than located on the surface as for Surface Permanent Magnet AC motors. MTPA works by introducing a small (compared to q-axis) negative d-axis current which takes advantage of reluctance torque of the IPM. Essentially, MTPA is maximizing the sum of magnetic and reluctance torque, rather than maximizing magnetic torque with zero d-axis current.
+MPTA is a control strategy to obtain the greatest torque out of IPM motors, which have a difference in their Q-axis and D-axis inductances. Specifically the quantity (Lq-Ld) is positive. This is due to the fact that an IPM's rotor's magnets are buried in the rotor, rather than located on the surface as for Surface Permanent Magnet AC motors. MTPA works by introducing a small (compared to q-axis) negative d-axis current which takes advantage of reluctance torque of the IPM. Essentially, MTPA is maximizing the sum of magnetic and reluctance torque, rather than maximizing just magnetic torque with zero d-axis current.
 ===Thermal Limiting===
 Losses in the motor and motor controller are a function of current. Therefore we need to reduce the current through the devices to limit the temperature of both the motor and controller.

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 ==Torque Regulation==
 ==Surface Mount Permanent Magnet Machines==
 ==Interior Permanent Magnet Machines==

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 </math>
 ==Current Regulation==
-A PI controller is commonly used to regulate the phase currents. This is explained by starting with a simple motor model in the DQ-frame (the motor is represented by a voltage source, resistance, and inductance).
+A PI controller is commonly used to regulate the currents. This is explained by starting with a simple motor model in the DQ-frame (the motor is represented by a voltage source, resistance, and inductance).
 <math>
 I_{dq} = \frac{V_{dq} - V_{emf}}{R_s + sL_{dq}}
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 </math>
 ==Torque Regulation==

← Older revision		Revision as of 00:08, 21 June 2022
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	===Resolvers & Encoders===		===Resolvers & Encoders===
		+	====Calibration====
		+
	==Space Vector PWM==		==Space Vector PWM==