Frank Jeske

Bio: Frank Jeske is an academic researcher from ebm-papst. The author has contributed to research in topics: Rotor (electric) & Electric motor. The author has an hindex of 16, co-authored 51 publications receiving 535 citations.

Magnetic Gear: Radial Force, Cogging Torque, Skewing, and Optimization

Abstract: Magnetic gears are able to transmit torque between an input and an output shaft without mechanical contact. As for electrical drives, torque density, acoustic noise, and torque ripple are of primary concern. This paper describes the influence of the pole numbers on the radial forces and the cogging torques. We show how continuous and discrete skewing can suppress torque harmonics effectively. Further, we investigated different simulation modes for magnetic gears using finite-element software. A multiobjective optimization was conducted to find a Pareto-optimal magnetic gear, whose cogging torque was minimized by skewing one rotor. Finally, we present a prototype with a gear ratio of 1:21, and compare finite-element results with the measurements of unskewed and skewed magnetic gears.

Analytical Stiffness Calculation for Permanent Magnetic Bearings With Soft Magnetic Materials

Abstract: According to Earnshaw's theorem, the ratio between axial and radial stiffness is always -2 for pure permanent magnetic configurations with rotational symmetry. Using highly permeable material increases the force and stiffness of permanent magnetic bearings. However, the stiffness in the unstable direction increases more than the stiffness in the stable direction. This paper presents an analytical approach to calculating the axial force and the axial and radial stiffnesses of attractive passive magnetic bearings (PMBs) with back iron. The investigations are based on the method of image charges and show in which magnet geometries lead to reasonable axial to radial stiffness ratios. Furthermore, the magnet dimensions achieving maximum force and stiffness per magnet volume are outlined. Finally, the calculation method was applied to the PMB of a magnetically levitated fan, and the analytical results were compared with a finite element analysis.

Method for controlling a physical variable in an electronically commutated motor, and motor for carrying out said method

Abstract: The invention relates to a method for controlling a physical variable in an electronically commutated motor, according to which the current is supplied to the stator winding arrangement (102) of the motor in the form of current blocks. The distance (BW) between switch-on command and cut-off command for controlling said current blocks, that is the length (BW) of the control signals, is influenced by a control device, and the current effective value of said current blocks is influenced by adjusting a duty factor (pwm). Upper and lower limits are set to the length (BW) of the control signals. When the control signal becomes shorter than a predetermined lower limit value, the duty factor (pwm) is reduced, thereby reducing the effective value of the current and increasing the length (BW) of the current blocks. When the control signal becomes longer than a predetermined upper limit value, the duty factor (pwm) is increased, thereby increasing the effective value of the current and reducing the length (BW) of the current blocks in compensation thereof.

Method for controlling the commutation in an electronically commutated motor, and an electronically commutated motor for carrying out said method

Abstract: The invention relates to a method for controlling the commutation in an electronically commutated motor (20), which has a stator with at least one phase (24, 26) and has a permanent magnet rotor (22) and to which a current limiter (36, 58) and a controller (18) for controlling a motor variable are assigned. The current limiter (36, 58) serves to limit the current (I) in the at least one phase (24, 26) to a default value. The controller (18) effects the controlling by changing the temporal interval (W) between switching on (t1) and switching off (t2) of the current (i1, i2) in the at least one phase. In this method, the default value, to which the current limiter limits the current (i1, i2) in the relevant phase, is variable. The default value is modified essentially according to a ratio (W/T) of two times, namely according to the ratio of the temporal interval (W) between switching on (t1) and switching off (t2) of the current (i1, i2) in the relevant phase to the length of time (T) the rotor requires at the instantaneous rotational speed to rotate about a given angle of rotation. This makes a noise reduction possible at low rotational speeds. The invention also relates to a corresponding motor.

Method and apparatus for DC motor speed control

Abstract: A memory device, e.g. a capacitor, is provided for a collectorless DC motor. This component is charged whenever a particular rotor position is reached. In so doing, a voltage value or quantity on this memory device is changed. This quantity is compared to another quantity, which is dependent on a desired parameter, e.g. ambient temperature or gas or dust concentration. A reference signal is produced when a particular reference criterion is satisfied. The difference between the beginning of this reference signal and a second predetermined rotor position, which follows the initial predetermined rotor position with respect to time, is measured, and on the basis of this measurement, the current flow of the collectorless DC motor is influenced or regulated. In particular, the current can be toggled on and off as the rotor passes certain predetermined positions.

Motor controller having a multifunction port

Abstract: In one aspect, a control circuit to control a speed of a motor includes a control logic circuit connected to a multifunction port. The control logic circuit is configured to receive a control signal provided at the multifunction port and to provide response signals based on the control signal to place the motor in at least two of a sleep mode, a brake mode and a pulse-width modulation (PWM) mode. The motor control circuit also includes an H-bridge circuit configured to control the motor based on the response signals.

Electric bending endoscope

Abstract: An electric bending endoscope includes a temperature sensor that detects the temperature of a motor as a state value indicating the driving state of a bending drive unit. A bending control device comprises: a temperature detection unit that receives the data of the temperature detected by the temperature sensor; a record unit in which the limits of motor temperature inputted in advance are recorded; a comparison unit that compares the data of the temperature sent from the temperature detection unit with the limits of motor temperature recorded in the record unit; and a notification unit that notifies that the driving state of a motor is approaching the limit.

Cooling module and related control circuits useful therefor incorporating a communication port for receiving digital command signals to control module

Abstract: A cooling module includes, for certain embodiments, a brushless DC fan and integral fan control circuitry which independently implements a self-contained start and run motor control loop and also includes a communications port to accept commands from a host processor and to provide status and other data in response to queries from the host processor. In one embodiment, a fan module interfaces with a two-wire serial bus, such as an I2C bus or SMbus, and accepts commands and provides status and data in a serial digital format. A variety of commands such as on/off, and various speed control settings may be received from the host system, and the actual speed of the fan may be reported back when queried by the host system. In some embodiments a temperature within or near the fan housing or of the air flow through the fan may be reported back when queried. The entire fan control circuit may preferably be incorporated within the fan housing, including a serial interface and power terminals for the fan, resulting in a compact four-wire interface for the fan module.

Multiple dimension position sensor

Abstract: An apparatus including a controller, a workpiece transport in communication with the controller having a movable portion and a transport path, and a multi-dimensional position measurement device including at least one field generating platen attached to the movable portion and at least one sensor group positioned along the transport path and in communication with the controller, the field generating platen is configured for position measurement and propelling the movable portion, each sensor in the at least one sensor group is configured to provide but one output signal along a single axis corresponding to a sensed field generated by the at least one field generating platen and the controller is configured calculate a multi-dimensional position of the movable portion based on the but one output signal of at least one of the sensors in the at least one sensor group, the multi-dimensional position including a planar position and a gap measurement.

Microcontroller methods of improving reliability in DC brushless motors and cooling fans

Abstract: A method of controlling a motor speed for a fan assembly includes receiving a duty cycle value at a microcontroller. The microcontroller receives a measured fan speed from a speed sensor. An expected fan speed is determined, where the expected fan speed corresponds to the duty cycle value. The measured fan speed is compared with the expected fan speed. A duty cycle of a motor driving signal is reduced if the measured fan speed is less than a predetermined fraction of the expected fan speed.