An external force estimation device is configured to estimate an external force acting on a motor. The external force estimation device includes a processor. The processor is configured to: calculate an output torque of the motor by using a value of a current supplied to the motor; estimate an inertia torque of the motor by using rotational position information of the motor; estimate a first friction torque of the motor by using the rotational position information of the motor; perform temperature-based correction for the first friction torque by using temperature information of the motor; and estimate the external force by subtracting the inertia torque and the first friction torque after the temperature-based correction from the output torque.

A method of speed control based on a self-learning model of load torque and a moment inertia is applied to a controller of controlling a motor. The method includes steps of: establishing a relationship between the load torque and the moment inertia by a self-learning manner, correspondingly acquiring a value of the moment inertia according to a value of the load torque, and adjusting parameters of the controller to control rotation of the motor according to the value of the moment inertia.

The purpose of the present invention is to provide a device monitoring technique having little restriction even on application to an already-existing device or facilitating monitoring even when a device to be monitored is in variable speed operation or under load variation. One of the representative device monitoring devices of the present invention monitors a device system using, as a power source, an AC electric motor driven by an inverter and is provided with a torque current estimation unit and a state estimation unit. The torque current estimation unit acquires information about AC currents of at least two phases and excitation current of the AC electric motor and calculates a torque current estimated value of the AC electric motor on the basis of the AC currents and the excitation current. The state estimation unit estimates the state of the device system from information including at least one of the feature amounts extracted from the torque current estimated value.

One or more example embodiments provide systems and methods for using impedance separation and impedance shaping.

An external force estimation device is configured to estimate an external force acting on a motor. The external force estimation device includes a processor. The processor is configured to: calculate an output torque of the motor by using a value of a current supplied to the motor; estimate an inertia torque of the motor by using rotational position information of the motor; estimate a first friction torque of the motor by using the rotational position information of the motor; perform temperature-based correction for the first friction torque by using temperature information of the motor; and estimate the external force by subtracting the inertia torque and the first friction torque after the temperature-based correction from the output torque.

A rotation speed assessment device (1) assesses suitability of a rotation speed of a motor (11) in a rotation device (10) having the motor (11) connected to an object to be rotated (20) to rotate the object to be rotated (20) and having a rotation control unit (13) controlling operation of the motor (11) and carrying out emergency stopping of the motor (11) when the motor (11) becomes uncontrollable. The rotation speed assessment device (1) has an inertia estimation unit (2) estimating an inertia of the motor (11) and object to be rotated (20), an assessment unit (3) assessing suitability of a planned rotation speed based on the inertia estimated by the inertia estimation unit (2), and a notification unit (4) providing a notification when the planned rotation speed is assessed as unsuitable by the assessment unit (3).

A method of speed control based on a self-learning model of load torque and a moment inertia is applied to a controller of controlling a motor. The method includes steps of: establishing a relationship between the load torque and the moment inertia by a self-learning manner, correspondingly acquiring a value of the moment inertia according to a value of the load torque, and adjusting parameters of the controller to control rotation of the motor according to the value of the moment inertia.

A hand-held electrically powered cut-off tool (100) for cutting concrete and stone by a rotatable cutting disc (105), the cut-off tool (100) comprising an electric motor (130) arranged to be controlled by a control unit (110) via a motor control interface (120), wherein the control unit (110) is arranged to obtain data indicative of an angular velocity of the cutting disc (105), and to detect a kickback condition based on a decrease in angular velocity, wherein the control unit (110) is arranged to determine an angular acceleration associated with the electric motor (130), and to detect the kickback condition based on a comparison between the determined angular acceleration and a detection threshold, wherein the detection threshold is configured at an angular acceleration between 5000 rad/s.sup.2 and 35000 rad/s.sup.2, and preferably between 10000 rad/s.sup.2 and 30000 rad/s.sup.2, and more preferably between 20000 rad/s.sup.2 and 30000 rad/s.sup.2.

A method for operating a drive train includes supplying a motor voltage to an electric motor by a converter for achieving a torque setpoint value, determining an angular velocity actual value and an angular acceleration actual value from values of the angular position of the rotor, determining the torque setpoint value from a moment of inertia and an angular acceleration setpoint value, which is determined as an actuation variable, determining the moment of inertia as the sum of the moment of inertia of the drive train without a load and the moment of inertia of the load, and determining the moment of inertia of the load from a torque actual value and from the angular acceleration actual value.

A hand-held electrically powered cut-off tool (100) for cutting concrete and stone by a rotatable cutting disc (105), the cut-off tool (100) comprising an electric motor (130) arranged to be controlled by a control unit (110) via a motor control interface (120), wherein the control unit (110) is arranged to obtain data indicative of an angular velocity of the cutting disc (105), and to detect a kickback condition based on a decrease in angular velocity, wherein the control unit (110) is arranged to control an electromagnetic braking of the electric motor (130) in response to detecting a kickback condition, wherein the control unit (110) is arranged to determine an angular acceleration associated with the electric motor (130), and to detect the kickback condition based on a comparison between the determined angular acceleration and a configurable detection threshold.