Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C32/00—Bearings not otherwise provided for
  • F16C32/04—Bearings not otherwise provided for using magnetic or electric supporting means
  • F16C32/0406—Magnetic bearings
  • F16C32/044—Active magnetic bearings
  • F16C32/0444—Details of devices to control the actuation of the electromagnets
  • F16C32/0446—Determination of the actual position of the moving member, e.g. details of sensors
  • F16C32/0448—Determination of the actual position of the moving member, e.g. details of sensors by using the electromagnet itself as sensor, e.g. sensorless magnetic bearings
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C32/00—Bearings not otherwise provided for
  • F16C32/04—Bearings not otherwise provided for using magnetic or electric supporting means
  • F16C32/0406—Magnetic bearings
  • F16C32/044—Active magnetic bearings
  • F16C32/0444—Details of devices to control the actuation of the electromagnets
  • F16C32/0451—Details of controllers, i.e. the units determining the power to be supplied, e.g. comparing elements, feedback arrangements with P.I.D. control
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C32/00—Bearings not otherwise provided for
  • F16C32/04—Bearings not otherwise provided for using magnetic or electric supporting means
  • F16C32/0406—Magnetic bearings
  • F16C32/044—Active magnetic bearings
  • F16C32/0444—Details of devices to control the actuation of the electromagnets
  • F16C32/0457—Details of the power supply to the electromagnets
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C39/00—Relieving load on bearings
  • F16C39/06—Relieving load on bearings using magnetic means

Definitions

• the invention relates to the sensorless orientation for a magnetic bearing. Such magnetic storage is used for
• the main advantage of a magnetic bearing over a conventional storage, for example, with a ball bearing, consists in the greatest degree of frictionlessness. This is particularly with regard to wear a pre ⁇ part.
• a storage of rapidly rotating rotors is only thus possible.
• One difficulty with electromagnetic bearings is that an electronic control of the position of the object to be stored is essential. To the determination of the Po ⁇ sition of the object is in principle quite necessary to the electromagnet.
• the direct determination of the speed at which a change in position is made can take place.
• the determination of the position is directly ei ⁇ nem position sensor.
• the use of a position sensor is associated with certain disadvantages.
• a position sensor raises additional costs for the installation of the sensor, a certain construction ⁇ space is required and the sensor, if it fails, may be responsible for a failure of the entire magnetic bearing system.
• an electromagnet When considering conventional magnetic bearings, an electromagnet exerts an attractive force on a floating body. This attraction act disruptive forces such as against the Ge ⁇ weight force of the floating body. It creates a balance of power at a certain distance. In Festge ⁇ convincedem current, the attractive force increases as the body approaches the electromagnet. It decreases as the body moves away from the electromagnet.
• the magnetic bearing is unstable due to the physical properties and must therefore be regulated.
• the information about the Be ⁇ wegungs the floating body relates ⁇ example, a controller of a position sensor. If there is a sensorless magnetic bearing, an external sensor is not required. Since a regulation is necessary even when sensorless magnetic bearing, for this purpose the necessary Positionsinformati ⁇ on is obtained by the air gap dependent properties of the electromagnets.
• FIG. 1 shows a schematic diagram of a magnetic bearing 10.
• a unidirectional bearing with an electromagnet 200 is considered.
• a pole 210 of the electromagnet 200, together with the object 100 to be stored, forms an air gap 20 whose length l changes as a function of the position r of the object 100.
• the inductance L of the magnetic bearing 10 is calculated in the form of the equation
• the inductance of the system is indirectly proportional to the distance of the object 100 from the poles of the electromagnet 200.
• This essential property forms the basis for many estimation and observation algorithms for determining the position of the object 100.
• the prior art references [2, 3, 4] should be mentioned.
• For sensorless operation of a magnetic levitation system there are a variety of tools whose essential approaches and advantages or disadvantages, for example.
• the inventive method for adapting a value ei ⁇ nes electrical resistance of a magnetic bearing comprises the following steps:
• the resistance adaptation consists of a low-pass filter and an I-controller.
• the inductance error AL is determined by means of an I-controller d - 1 -
• the inventive method for sensorless position detection of an object mounted in a magnetic bearing relative to the magnetic bearing, in particular relative to an electromagnet of the magnetic bearing comprises the following steps:
• a velocity of the object is also calculated from the estimated inductance values llf, ll.
• respective current initial condition i ⁇ 0 determined and a Stromendbe conditions ⁇ i N _ tj.
• the position estimate considered in this invention is based on the identification of the current inductance value L (r) with the aid of which the current position r of the object to be stored can be recalculated.
• no additional measurement signal such as a sinusoidal, is fed into the control of Spu ⁇ le, but it is carried out directly with a pulse width modulated voltage control.
• the estimation algorithm developed in this invention essentially consists of a least-squares estimator for determining the inductance in the individual PWM phases, ie in the charging and discharging phases. As shown below, this least-squares estimator can be further divided into two sub-tasks, resulting in a highly effi ⁇ cient implementation. Furthermore, a model-based calculation of the position and / or speed of the object to be stored can be used.
• FIG. 1 shows a schematic diagram of a magnetic bearing, showing an electrical equivalent circuit diagram of a mag netic levitation system and an associated Dia ⁇ gram with charging and discharging the coil, shows the charging and discharging the coil current i at pulse width modulated voltage supply PWM.
• the magnetic co-energy is defined
• FIG. 1 To briefly illustrate the problem solved in this invention, the electrical equivalent circuit diagram of a simple magnetic bearing is shown in FIG.
• R is the effective electrical resistance of the coil and the leads
• ⁇ PWM is the applied pulse width modulated voltage
• T D P r W, M M are the two phases
• Period of the pulse width modulated voltage and with 0 ⁇ ⁇ 1 denotes the duty cycle, ⁇ therefore indicates the ratio of the durations of the first and the second phase. This results in about a current waveform as shown in the right side of Figure 2.
• the task of the position estimation is to estimate a value of the inductance in the first step from the measurements of the current and the voltage and to determine the position r from this.
• the particular difficulty is to realize this as independently as possible from the other influencing factors.
• Least-squares estimator / estimator according to the principle of least squares
• the Indukt foundeds based on the law of induction, the electric dynamics, illustrating by means of a time discretization equidistant as in Figure 3 so sto is ⁇ rides that a linear least-squares method for the recursive determination of the inductance can be applied.
• FIG. 3 shows the time profile of the current i in the first and in the second phase.
• the least-squares method can be established in the form of a Multiratenver- proceedings so that's calculated to be determined entries of the so-called regres- sors with a small sample ⁇ time T and then select the Reg- tion, ie the determination of the partial inductances and the start and end conditions of the current, with a much larger sampling time T r , which is generally an integer multiple of the period of the PWM, can be made.
• equation (7) can be expressed in the form
• L (r) are negligible over a PWM period, i.
• the above calculations can be split between a fast calculation on a fixed point processor and a slow calculation on a floating point processor.
• L is the mean value of L (t) to be estimated. If one continues to carry the mean currents over a Sectionperio ⁇ de
• the mean inductance to be estimated is calculated accordingly
• the speed w is often required.
• this is determined by approximating the estimated position f.
• this approach has the disadvantage that measurement noise is very noisy
• the computation can be divided into a mathematically very simple part, which must be calculated with a fast sampling time, and a complex part, which can be determined with a much shorter sampling time. This represents, in particular with regard to a cost-effective implementation, a substantial advantage over conventional methods.
• the electrical resistance required for the sensorless state estimation of the magnetic bearing is adapted on the basis of the resistance- dependent, estimated inductance error.
• L n is the mean of L n (t) to be estimated. If one continues to carry the average energy values over a partial period
• a resistance adaptation is proposed, which is based on the fact that the estimation of an inkorrek ⁇ ten resistance value in the estimated inductance error
• Equation (41) directly proportional to the resistance error 5R is.
• the change in resistance caused by the heating of the electromagnet is much slower than that
• the resistor adaptation thus consists of a low-pass filter and an I-controller.
• the resistance adaptation consisting of
• Equations (44) and (45) based on the inductance error of the least-squares-based position estimate ensures that the resistance error 5R is regulated to zero so as to estimate the real resistance value.
• T LF and ⁇ ⁇ are positive setting parameters .
• equations (44) and (45) are time discretized. However, the discretization is not clear. In the simplest case we replace the continuous differentiation by the forward difference quotient (Euler forward method). From this one obtains a so-called difference equation. With the help of which can in equidistant time steps from the previous
• Estimate a new one can be calculated.
• the Estimated Resistance value is passed to the position estimate, which computes a new estimate of the inductances and yields a new estimate of the inductance error. This iteration is performed in each sampling from ⁇ .
• the method does not require additional hardware outlay for the reconstruction of the state variables, since inherent measuring effects are caused utilized by the pulse-width-modulated driving of ⁇ . Only a current and voltage measurement must be available. If the algorithm is combined with an observer, then it is possible to algorithmically separate the entire system from an systems theory viewpoint into an electrical and mechanical subsystem and, moreover, to use the full model information of the overall system for obtaining the state.
• the separate treatment of the charging and discharging process for the life-squares estimation of the inductances offers the possibility of reducing the influence of the integrator drift due to the discretization of the law of induction.
• the transient disturbance behavior of the non-ideal electrical switching elements of the inverter during switching on and off and the influence of eddy currents in the software implementation can be excluded.
• the computational effort can be substantially reduced.
• the computation of the regressors can be done in integer arithmetic cost-effectively on programmable integrated circuit
• Circuits e.g., FPGA
• FPGA field-programmable gate array
• the Posi ⁇ tion regulator which is usually made of a compensation of non-linearities and a stabilizing proportional integral-differential controller is conventionally le- diglich returned to the estimated position and formed in the Diffe ⁇ ential portion of the controller a speed-proportional signal.
• the noise of the position estimate affects and limits the achievable control quality and robustness against model uncertainties of the controller. If, as in the developed estimation methods, in addition, a speed estimate available, it can also returned and an increase in control quality and robustness are targeting it ⁇ .
• the mechanical part of the model Intelsys ⁇ tems can be incorporated into the state estimation with a nonlinear model-based Beboachterford.
• a filtering for noise suppression of the determined from the least-squares estimator Position and speed-dtechniks since it is possible and on the other hand, by receiving a Stördorfnansatzes in the model equations a force acting from the outside ⁇ SEN load power estimated.
• the observer-based filtering does not involve a phase shift.
• the invention enables a separate estimation of the inductance of the charging and discharging phase with the aid of least-squares estimation, wherein a separation into a fast but mathematically simple part and a slow mathematically more complex part can take place.
• the influence of the speed of the object to be stored and a change in the pulse width of the voltage can be eliminated by a suitable correction.
• the speed of the object to be stored can be determined directly without time differentiation of the position from the estimated values of the inductance and further auxiliary quantities.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Mechanical Engineering (AREA)
• Magnetic Bearings And Hydrostatic Bearings (AREA)
• Measurement Of Resistance Or Impedance (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

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• 2010
  • 2010-04-01 DE DE102010013682.4A patent/DE102010013682B4/de active Active
• 2011
  • 2011-03-08 EP EP11710444A patent/EP2553284A1/de not_active Withdrawn
  • 2011-03-08 US US13/636,630 patent/US8970079B2/en active Active
  • 2011-03-08 WO PCT/EP2011/053423 patent/WO2011120764A1/de active Application Filing
  • 2011-03-08 KR KR1020127028573A patent/KR101824749B1/ko active IP Right Grant
  • 2011-03-08 JP JP2013501713A patent/JP5661914B2/ja active Active
  • 2011-03-08 CN CN201180016689.1A patent/CN102812262B/zh not_active Expired - Fee Related

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