Glossary
Glossary: drive technology and simulation
The most important terms around electric drives, inverters, CAN and real-time simulation – briefly explained, the way we use them at Persystems.
Terms: Active Short Circuit (ASC) · Arm / disarm · Back-EMF · BLDC · Block commutation · CAN bus · CAN identifier (29-bit) · Continuous power · Co-simulation · DC link · Derating · d/q transformation · DroneCAN · ESC · esc.Status · Field-oriented control (FOC) · Field weakening · FMI / FMU · Hall sensors · Hardware-in-the-loop (HiL) · Id / Iq · Inverter · Model-in-the-loop (MiL) · Node ID (DroneCAN) · NodeStatus · PersyCAN · Phase current · PMSM · PWM / PPM · Recuperation · Safe Torque Off (STO) · Saturation · Sensorless operation · Software-in-the-loop (SiL) · Space-vector modulation · Structure-preserving integrators · Switching ripple · Telemetry
Active Short Circuit (ASC)
Safe reaction of an inverter in the event of a fault: the motor phases are actively short-circuited so the motor brakes without feeding voltage back into the DC link. Configurable in the INV-60V-120A as an alternative to Safe Torque Off.
Arm / disarm
Enable or block the drive. A disarmed inverter does not execute setpoints. In the INV-60V-120A via CAN or input.
Back-EMF
The voltage induced in the stator winding by the rotating rotor. It rises with speed and limits the maximum speed at a given DC-link voltage. In sensorless operation it is used to determine the rotor position.
BLDC
Brushless DC motor – usually a permanent-magnet synchronous motor operated with block commutation. The same motor can be run with field-oriented control; then it is usually called a PMSM.
Block commutation
Control scheme in which two of the three phases carry current and the pattern switches every 60 electrical degrees (“six-step”). Simple, but with torque ripple and higher losses than field-oriented control.
CAN bus
Serial fieldbus (Controller Area Network) with two wires (CAN High, CAN Low) and termination resistors, to which all participants are connected in parallel. Basis of PersyCAN and DroneCAN.
CAN identifier (29-bit)
Identifier of a CAN message, 29 bits long in the extended format (CAN 2.0B). PersyCAN places the device address in the identifier: commands to 0x0n000000, telemetry from 0x1n0000xx.
Continuous power
Power a drive can deliver without limit under defined conditions (cooling, ambient temperature) without a protection function stepping in. The sizing figure, as opposed to peak power.
Co-simulation
Coupling of several simulation tools or models that compute alternately and exchange data – for example a vehicle model in CarMaker and a drive model as an FMU.
DC link
DC side of the inverter between battery and power stage, supported by capacitors. DC-link voltage and DC current determine the load on the battery.
Derating
Controlled reduction of the permissible power with rising temperature so the drive keeps running instead of shutting down. The INV-60V-120A works with thermal derating logic.
d/q transformation
Mathematical conversion of the three phase currents into two components of a coordinate system rotating with the rotor: Id (flux-producing) and Iq (torque-producing). Core of field-oriented control.
DroneCAN
Open CAN protocol of the ArduPilot and PX4 world (formerly UAVCAN v0) for flight controller, ESCs, sensors and servos. The INV-60V-120A reports esc.Status at 10 Hz and NodeStatus at 1 Hz.
ESC
Electronic speed controller – motor controller for brushless motors, mainly in the RC and drone world. The INV-60V-120A is an inverter with field-oriented control that takes the ESC role over DroneCAN or PWM.
esc.Status
DroneCAN message with the operating data of an ESC, sent by the INV-60V-120A at 10 Hz.
Field-oriented control (FOC)
Control method in which the stator current is controlled in the rotating d/q system. Result: sinusoidal currents, smooth torque, precise torque limit. See the FOC guide.
Field weakening
Operation above the speed at which the back-EMF reaches the available voltage: a negative Id weakens the rotor field and allows higher speeds at reduced torque.
FMI / FMU
Functional Mock-up Interface: standard for exchanging and coupling simulation models. A Functional Mock-up Unit (FMU) is a model package according to this standard. OverDrive is delivered as an FMU and runs in Simulink, CarMaker and other FMI environments.
Hall sensors
Magnetic position sensors in the motor that provide the rotor position in coarse steps. The INV-60V-120A works sensorlessly or with a sin/cos or incremental encoder.
Hardware-in-the-loop (HiL)
Test stage in which a real control unit runs against a real-time simulator of the plant.
Id / Iq
The two components of the stator current in the d/q system: Iq produces torque, Id affects the flux. The INV-60V-120A sends actual and setpoint values of both currents as telemetry.
Inverter
Power electronics that convert the DC voltage of the DC link into the three-phase AC voltage for the motor – in the INV-60V-120A with one transistor pair per phase and field-oriented control.
Model-in-the-loop (MiL)
Test stage in which the control algorithm is computed as a model against a model of the plant – proof of concept before implementation.
Node ID (DroneCAN)
Address of a node on the DroneCAN bus. The INV-60V-120A gets it allocated dynamically; up to 20 ESC indices per bus.
NodeStatus
DroneCAN message with which a node reports its operating and health state (OK, Warning, Error, Critical). Sent by the INV-60V-120A at 1 Hz.
PersyCAN
CAN protocol of the Persystems inverters for setpoints, parameters, telemetry and firmware updates, with 29-bit identifiers and device address; dynamic address allocation through the discovery mechanism, like the node allocation in DroneCAN. See the PersyCAN page.
Phase current
Current between inverter and motor in one of the three phases. Determines torque and losses; not to be confused with the DC current from the battery.
PMSM
Permanent-magnet synchronous motor. Same construction as the “BLDC” motor; the term emphasizes operation with sinusoidal currents and field-oriented control.
PWM / PPM
Pulse-width modulation (PWM) or pulse-position modulation (PPM). As a setpoint signal the classic ESC control; as a modulation method the way the inverter forms the motor voltage from the DC-link voltage.
Recuperation
Operating the drive as a generator: braking energy flows back into the battery, the DC-link voltage rises briefly.
Safe Torque Off (STO)
Safe reaction in the event of a fault: the power stage is switched off and the motor coasts freely. Configurable in the INV-60V-120A as an alternative to Active Short Circuit.
Saturation
Nonlinear effect in the motor iron: at high currents the inductance drops. Changes the controller dynamics and must be part of a model for firmware validation – OverDrive computes saturation.
Sensorless operation
Determining the rotor position without a position sensor, from the motor model and the back-EMF. Standard in the INV-60V-120A; alternatively a sin/cos or incremental encoder.
Software-in-the-loop (SiL)
Test stage in which the real firmware runs against a model of motor, power stage and load – without hardware, on the development PC. See the SiL guide.
Space-vector modulation
Modulation method that computes the switching pattern of the six transistors from the desired stator voltage. Standard with field-oriented control.
Structure-preserving integrators
Integration methods from geometric mechanics that preserve the structure of the physical system and thereby conserve energy, momentum and charge. The numerical foundation of OverDrive.
Switching ripple
Superimposed current fluctuation at the inverter’s switching frequency. Lookup-table models do not know it; OverDrive resolves it (±0.2 A in the benchmark, matching LTspice, PLECS and Simulink).
Telemetry
Cyclically sent operating data of the drive. The INV-60V-120A sends currents, voltages, temperatures, speed, torque and status every 100 ms over PersyCAN.