A safety apparatus and method for monitoring the position of a servo joint in a servo joint driving system are introduced. The safety apparatus includes modules for measuring powerline signals to determine a servo motor position and/or speed safely. By analyzing the synchronization between the motor and powerline signals, loss of synchronization, unexpected resistance experienced by the motor, and other fault conditions are detected so that power can be cut from the servo motor for safety. The safety apparatus and method achieve a functional safety position and/or speed generating and monitoring and reduce reliance on expensive position sensors and encoders. Robots utilizing the safety apparatus and a method of its use are also disclosed.

A power converter is configured to measure an output current and to determine a multi-phase voltage reference as a function of the output current. Within the same switching period the voltage reference is determined, a modulation routine determines a modulation index for each phase of the output voltage. In some instances, one or more phases must start modulation during the switching period before the new modulation index is determined. The modulation routine stores the value of the modulation index generated from the prior switching period and uses the stored value when a new value is not yet ready. An offset value for the phase voltage which used a modulation index from the prior switching period is determined in order to compensate the phase voltages of the other phases and to maintain a desired line-to-line voltage output from the power converter.

A method for determining at least one current fed to an electrical machine of a drive system includes predefining a carrier frequency of the at least one current fed to the electrical machine, detecting an electromechanical feedback signal dependent on the at least one current, at a link circuit capacitor of the drive system, identifying a signal component associated with the at least one current in the feedback signal on the basis of the predefined carrier frequency, and determining the at least one current fed to the electrical machine on the basis of the signal component.

A control device includes: a current detector that detects rotating electrical machine currents flowing to the rotating electrical machine; a position estimator that estimates a rotor position of the rotating electrical machine based on the rotating electrical machine currents; a controller that calculates drive voltage commands based on the rotating electrical machine currents and information on the rotor position, adds position estimation voltage commands and the drive voltage commands to obtain rotating electrical machine voltage commands. The position estimator extracts position estimation currents included in the rotating electrical machine currents, the position estimation currents being changed according to the position estimation voltage commands, and estimates the rotor position of the rotating electrical machine using a DC component of amplitudes of the position estimation currents extracted, the DC component being not changed according to the rotor position.

A motor drive method is a method of driving a motor by a motor drive apparatus. The motor drive apparatus includes an inverter that regulates supply power to the motor that is a synchronous machine and includes a controller that controls the inverter. The method includes changing, before loss of synchronism, a speed of the motor from a second speed range to a first speed range. A speed range in which the motor is operable at a substantially fixed speed is the first speed range, and a speed range that is lower than the first speed range and includes zero speed is the second speed range.

A method for phase-voltage based motor period measurement includes generating a commanded phase voltage and applying the commanded phase voltage to a first phase voltage input of an electric motor, a second phase voltage input of the electric motor, and a third phase voltage input of the electric motor, measuring a first period of a phase voltage associated with the first phase voltage input and the second phase voltage input and comparing the measured first period to a frequency of the commanded phase voltage, and, in response to a determination that the measured first period of the phase voltage associated with the first phase voltage input and the second phase voltage input is outside of a range of the frequency associated with the commanded phase voltage, identifying a fault associated with the first integrated circuit or signal path.

In one aspect, a system for determining an initial angular position of a rotor of a synchronous machine includes a motor driver module configured to provide a motor driver voltage signal to the synchronous machine, the motor driver voltage signal being sufficient to induce an electrical current in the synchronous machine; and a rotor position determination module configured to receive an indication of the current generated in the machine and to determine the initial position of the rotor based on the indication of the current generated in the machine. The motor driver voltage signal includes at least a first portion, a second portion, and a third portion, the first portion has a first non-zero voltage during a first temporal duration, the second portion has a second non-zero voltage during a second temporal duration, and the third portion has a substantially zero voltage during a third temporal duration, the first portion has a first polarity and the second portion has a second polarity that is opposite to the first polarity, and the first temporal duration and the second temporal duration are different.

A control device for an electric motor includes a control circuit that controls an operation of an inverter circuit on the basis of a voltage command value corresponding to a difference between a current command value calculated on the basis of the position of a rotor of the electric motor, and a current flowing through the electric motor. A current estimation unit estimates the current flowing through the electric motor by substituting the voltage command value, a parameter unique to the electric motor, and a rotational speed calculated on the basis of the position of the rotor into a voltage equation serving as a model of the electric motor. An LR estimation unit estimates an inductance and a resistance of the electric motor serving as parameters on the basis of the difference between the current obtained by a current acquisition unit and the current estimated by the current estimation unit.

A system and method for controlling an electric machine via an inverter comprises an speed estimator that is configured to estimate a rotor speed of an electric motor to determine whether to control the inverter to operate the electric motor in a first mode or a second mode. For example, the first mode comprises a current-frequency control mode and the second mode comprises a back electromagnetic force (BEMF) mode. An electronic data processor or controller is configured to determine a first (current) command associated with a first mode of operating the electric motor, if the estimated rotor speed is a less than a speed threshold. The electronic data processor or controller is configured to determine a second (current) command associated with a second mode of operating the electric motor if the estimated rotor speed is equal to or greater than the speed threshold.

Proposed is a method of diagnosing abnormality of sensorless control of a motor for an air compressor, the method including estimating a speed of a motor in real time when a motor starts determining whether or not a preset condition for activating a function of diagnosing abnormality of sensorless control is satisfied, from a slope of the estimated speed of the motor performing control for decreasing an amount of electric current to be applied to the motor, in a case where the preset condition is satisfied computing an amount of decrease in the slope of the estimated speed of the motor while the amount of the electric current is decreased; and determining whether or not the sensorless control fails, by comparing the amount of the decrease in the slope of the speed of the motor with a preset value for confirming diagnosis of the abnormality of the sensorless control.