EP0976675B2 - Method of force limitation for automatic elevator doors - Google Patents

Abstract

The drive force profile in normal operation, interfering forces being absent, is determined from a mathematical model. This profile is compared with the actual drive force measured during use. Departures of given magnitude, which are triggered by mechanical interference, stop or reverse door travel.

Description

The invention relates to a method for limiting the force for automatic elevator doors with a door drive consisting of control, motor and drive mechanism for moving a car door and a landing door according to the door position corresponding speed curve and force curve from an open position to a closed position or vice versa, the force curve itself Over the course of time, changing door parameters can be adapted and the doors can be stopped and / or reversed during the movement process in the event of an interference force triggered by an obstacle.

From the Patent DE 39 21 158 a control device for a DC motor driven articulated door is known. The drive torque is proportional to the motor armature current. In a memory device, the motor current profile is stored as a function of the angle of rotation of the door in trouble-free operation and with the maximum permissible torque. These current values can be obtained by computation or experiment. In order to take account of frictional losses acting on the door, the above-mentioned current value is added with a moving average, which results from the actual value of the armature current in the obstacle-free operation, to form the setpoint armature current. The determination of the setpoint is provided after each perfect opening and closing of the door. If an obstacle occurs at the door, the actual value of the armature current increases disproportionately. In the control device, this actual value is compared with the desired value. If the actual value is above the permissible setpoint, the armature current and thus the door drive torque are reduced.

A disadvantage of the known device lies in the complex and extensive storage of the necessary for the average position-dependent current waveforms for the entire driving range of the door.

From the JP 09323877 a method for limiting the closing force in elevator doors is known in which an elevator door model of a displacement value of the door motor and a motor speed, the motor drive torque calculated taking into account further parameters.

In a comparator, the calculated motor is compared with a torque command of a speed control. If the difference between the compared values exceeds a deviation tolerance value, a reversing command is issued for the door.

On this basis, it is an object of the present invention to provide an alternative method for limiting the closing force in elevators. The object is achieved by a method having the features of claim 1.

The advantages achieved by the invention are essentially to be seen in the fact that a compact form of the description of the noise-free drive power curve is possible. Thus, an automatic, optimal setting of the drive force limit can be achieved and the commissioning effort can be reduced. It is also advantageous that a force limit value is not only available for a specific desired speed function of the door, but can also be provided for deviating progressions, for example at reduced speed or increased acceleration, without first carrying out a new learning run.

When closing the door there is a risk that obstacles such as persons or objects can be located and trapped in the increasingly smaller door gap. When the door opening process, there is a risk that, for example, children's hands or flat objects can get between the mutually sliding door or between the door and the door frame.

The inventive method refers to the door closing process as well as the door opening process. Force limitation means the closing of the door, a limitation of the closing force or a limitation of the opening force during the opening process. Force curve refers to the force curve during the door closing process or during the door opening process.

Fig. 1

eine schematische Darstellung des erfindungsgemässen Verfahrens und

Fig. 2

statistische Funktionen zur Auswertung der Differenz zwischen Soll- und Istschliesskraftwerten.

In the following the invention will be explained in more detail with reference to an embodiment illustrative drawings. Show it:

Fig. 1

a schematic representation of the inventive method and

Fig. 2

Statistical functions for evaluating the difference between the target and actual closing force values.

Fig. 1 shows a system for the operation of an automatic elevator door consisting of a setpoint generator 1 for the speed, an actual value detector 2 speed / door position, a movement controller 3, a speed generator 4 in the form of a door drive consisting of control, motor and drive mechanism and an actual value detector 5 for the generated or applied driving force. When driving or engine power while applied by the engine, taking into account the realized gear ratios translated to the door force is called. The closing force or opening force is that force which is exerted on an obstacle during a closing or opening process from the door edge or door. A driving force model 6 for the driving force calculates the in the no-disturbance due to a mathematical model and the determined door parameters Operation to be applied driving force. A limit generator 7 calculates from the driving force model value and an allowable disturbance force a force limit, which is compared by means of a comparator 8 to the actual value of the driving force or the applied driving force. When the force limit value is exceeded, the door is stopped and / or a reversing movement is triggered.

With the aid of a mathematical model of the door and drive components involved, the drive force model 6 provides the driving force to be expended. This mathematical model uses motion equations and the previously determined door parameters to determine the driving force to be applied at normal acceleration and at a certain speed under normal, undisturbed conditions. The force limit value is calculated from the applied drive force and the maximum permissible disturbance force. If the door encounters an obstacle during the movement, stopping and / or reversing the elevator door is triggered when the force limit value is exceeded by the applied driving force, in order to ensure the safety of the elevator users.

The mathematical model can be fixedly set or adaptively designed in a further embodiment variant, with an adaptation to the parameter changes occurring during operation.

The model can be realized (explicitly) based on differential equations. The explicit mathematical model is based on Newton's equations of motion for door mechanics. These are given here for a simplified model of the door mechanism.

wobei

v̇_T

die Beschleunigung,

v_T

die Geschwindigkeit der Türkante,

F_MT

die vom Motor aufgebrachte, unter Berücksichtigung der kraftübertragenden und kraftumformenden Mechanik auf die Türkante/Tür umgerechnete Antriebskraft,

F_R

die als konstant angenommene Summe aller auf die Türkante umgerechneten Gleit- und Rollreibungskräfte der Türmechanik,

sign(v_T)

die Signumfunktion, die für v_T>0 den Wert 1 und für v_T<0 den Wert -1 aufweist,

g

die Schwerebeschleunigung 9,81 m/s²,

m_G

die Masse des Gegengewichtes und

m_GT

die Summe der unter Berücksichtigung der kraftübertragenden und kraftumformenden Mechanik auf die Türkante/Tür umgerechneten Massen aller bewegten Teile (Türflügel, Rollen, Zahnriemen, Riemenscheiben, Stahlseile, Gegengewicht, Rotor des Motors, usw.) bedeuten.

For the following considerations, all forces and velocities in the sense of direction of the closing door are positively defined. If the mechanism is modeled as a single-mass system with the total door mass m _GT converted to the door edge, the following relationship between velocity and force results (Newton's equation of motion, assuming direct force transmission between counterweight and door edge): $${\dot{\mathrm{v}}}_{\mathrm{T}}=\frac{{\mathrm{F}}_{\mathrm{MT}}-{\mathrm{F}}_{\mathrm{R}}\cdot \mathrm{sign}\left({\mathrm{v}}_{\mathrm{T}}\right)+\mathrm{G}\cdot {\mathrm{m}}_{\mathrm{G}}}{{\mathrm{m}}_{\mathrm{GT}}}$$

in which

v̇ _T

the acceleration,

v _T

the speed of the door edge,

F _MT

the driving force applied by the engine, converted to the door edge / door, taking into account the force-transmitting and force-transforming mechanism,

F _R

the sum of all sliding and rolling friction forces of the door mechanism converted to the door edge, assumed to be constant,

sign (v _T )

the signum function, which has the value 1 for v _T > 0 and the value -1 for v _T <0,

G

the gravitational acceleration 9.81 m / s ² ,

m _G

the mass of the counterweight and

m _GT

the sum of the masses of all the moving parts (door leaves, rollers, toothed belts, pulleys, steel cables, counterweight, rotor of the motor, etc.) converted into the door edge / door, taking into account the force-transmitting and force-transforming mechanism.

$${\dot{\mathrm{v}}}_{\mathrm{T}}=\frac{{\mathrm{v}}_{\mathrm{T}}\left(\mathrm{t}\right)-{\mathrm{v}}_{\mathrm{T}}\left(\mathrm{t}-\mathrm{T}\right)}{\mathrm{T}}$$

By switching to the force F _MT one obtains: $$\mathrm{FMT}={\dot{\mathrm{v}}}_{\mathrm{T}}\cdot {\mathrm{m}}_{\mathrm{GT}}+{\mathrm{F}}_{\mathrm{R}}\cdot \mathrm{sign}\left({\mathrm{v}}_{\mathrm{T}}\right)+\mathrm{G}\cdot {\mathrm{m}}_{\mathrm{G}}$$

$${\dot{\mathrm{v}}}_{\mathrm{T}}=\frac{{\mathrm{v}}_{\mathrm{T}}\left(\mathrm{t}\right)-{\mathrm{v}}_{\mathrm{T}}\left(\mathrm{t}-\mathrm{T}\right)}{\mathrm{T}}$$

This is a mechanical door model in explicit form, in which the physical parameters are still recognizable as such.

According to the equation given, the driving force to be applied at any time can be calculated as a function of the parameters and the acceleration v̇ _T. The acceleration is calculated approximately from the velocity values as shown in equation [3], where T is a suitably selected sampling time.

The equations [2], [3] can be easily programmed and provide the force model force monitoring value. Are the parameters F _R , m _G and m _GT unique, for example, in the production or in the Commissioning the door, fixed, so it is a fixed model. If the parameters of the model are automatically adjusted to the actual parameters of the door mechanism during operation of the door, this is called an adaptive model.

The setpoint generator 1 generates a speed setpoint as a function of time or path or door position. The motion controller 3 may be, for example, a speed / position controller that generates a speed command based on measured speed / position information.

The mathematical model establishes the dependence of the respective generated driving force on the acceleration, the speed setting and the door position. The mathematical model calculates the engine power that generates the given speed curve without any obstacle. This normal course depends, for example, on the given acceleration, the characteristic of the speed generation, the friction forces, the mass of the moving parts and on the parameters of the mechanics and the friction conditions in the mechanics.

The driving force generated by the driving force model 6 is subject to wear and aging changes during operation of the door. Therefore, the driving force model 6 can be designed so that a slow adaptation of the applied driving force takes place on the course subject to the changes. The actual value of the driving force or the applied driving force can be evaluated in conjunction with the target / actual speed to determine the effective, moving mass, the closing weight of the door and the friction force once or continuously during operation.

In order to obtain the unknown physical parameters of the explicit model, test runs are carried out in which the measured values for the engine power converted to the door edge / door and the speed of the door edge / door are periodically recorded and stored. According to equation [1], the acceleration depends on the engine power. The right side of equation [1] contains a force linear and a constant component. $${\dot{\mathrm{v}}}_{\mathrm{T}}=\frac{1}{{\mathrm{m}}_{\mathrm{GT}}}\cdot {\mathrm{F}}_{\mathrm{MT}}+\frac{-{\mathrm{F}}_{\mathrm{R}}\cdot \mathrm{sign}\left({\mathrm{v}}_{\mathrm{T}}\right)+\mathrm{G}\cdot {\mathrm{m}}_{\mathrm{G}}}{{\mathrm{m}}_{\mathrm{GR}}}\mathrm{a}\cdot {\mathrm{F}}_{\mathrm{MT}}+\mathrm{b}$$

$${\mathrm{m}}_{\mathrm{GT}}=\frac{1}{{\mathrm{a}}_{\mathrm{s}}}=\frac{1}{{\mathrm{a}}_0}$$

$${\mathrm{b}}_{\mathrm{s}}=\frac{-{\mathrm{F}}_{\mathrm{R}}\cdot \mathrm{sign}\left({\mathrm{v}}_{\mathrm{T}}\right)+\mathrm{g}\cdot {\mathrm{m}}_{\mathrm{G}}}{{\mathrm{m}}_{\mathrm{GT}}}=\frac{-{\mathrm{F}}_{\mathrm{R}}\cdot (-1)+\mathrm{g}\cdot {\mathrm{m}}_{\mathrm{G}}}{{\mathrm{m}}_{\mathrm{GT}}}$$

$${\mathrm{b}}_0=\frac{-{\mathrm{F}}_{\mathrm{R}}\cdot \mathrm{sign}\left({\mathrm{v}}_{\mathrm{T}}\right)+\mathrm{g}\cdot {\mathrm{m}}_{\mathrm{G}}}{{\mathrm{m}}_{\mathrm{GT}}}=\frac{-{\mathrm{F}}_{\mathrm{R}}\cdot (-1)+\mathrm{g}\cdot {\mathrm{m}}_{\mathrm{G}}}{{\mathrm{m}}_{\mathrm{GT}}}$$

$${\mathrm{m}}_{\mathrm{G}}=\frac{({\mathrm{b}}_{\mathrm{s}}+{\mathrm{b}}_0)\cdot {\mathrm{m}}_{\mathrm{GT}}}{2\mathrm{g}}$$

$${\mathrm{F}}_{\mathrm{R}}=\frac{({\mathrm{b}}_{\mathrm{s}}+{\mathrm{b}}_0)\cdot {\mathrm{m}}_{\mathrm{GT}}}{2}$$

If the variables v _T and F _{MT are recorded} over time for an opening or closing operation, the coefficients a and b of the linear equation [4] can easily be determined, for example by means of linear regression. The determined values for a closing process are with a _s and b _s , which are designated for an opening process with a ₀ and b ₀ . Then: $${\mathrm{a}}_{\mathrm{s}}={\dot{\mathrm{a}}}_0=\frac{1}{{\mathrm{m}}_{\mathrm{GT}}}$$

$${\mathrm{m}}_{\mathrm{GT}}=\frac{1}{{\mathrm{a}}_{\mathrm{s}}}=\frac{1}{{\mathrm{a}}_0}$$

$${\mathrm{b}}_{\mathrm{s}}=\frac{-{\mathrm{F}}_{\mathrm{R}}\cdot \mathrm{sign}\left({\mathrm{v}}_{\mathrm{T}}\right)+\mathrm{G}\cdot {\mathrm{m}}_{\mathrm{G}}}{{\mathrm{m}}_{\mathrm{GT}}}=\frac{-{\mathrm{F}}_{\mathrm{R}}\cdot (-1)+\mathrm{G}\cdot {\mathrm{m}}_{\mathrm{G}}}{{\mathrm{m}}_{\mathrm{<figure-callout\; id="0"\; label="GT\; b"\; filenames="imgf0001.png"\; state="\{\{state\}\}">GT\; </figure-callout>}}}$$

$${\mathrm{b}}_{}$$$${\mathrm{}}_0=\frac{-{\mathrm{F}}_{\mathrm{R}}\cdot \mathrm{sign}\left({\mathrm{v}}_{\mathrm{T}}\right)+\mathrm{G}\cdot {\mathrm{m}}_{\mathrm{G}}}{{\mathrm{m}}_{\mathrm{GT}}}=\frac{-{\mathrm{F}}_{\mathrm{R}}\cdot (-1)+\mathrm{G}\cdot {\mathrm{m}}_{\mathrm{G}}}{{\mathrm{m}}_{\mathrm{GT}}}$$

$${\mathrm{m}}_{\mathrm{G}}=\frac{({\mathrm{b}}_{\mathrm{s}}+{\mathrm{b}}_0)\cdot {\mathrm{m}}_{\mathrm{<figure-callout\; id="2"\; label="GT"\; filenames="imgf0001.png"\; state="\{\{state\}\}">GT</figure-callout>}}}{2\mathrm{G}}$$

$${\mathrm{F}}_{\mathrm{R}}=\frac{({\mathrm{b}}_{\mathrm{s}}+{\mathrm{b}}_0)\cdot {\mathrm{m}}_{\mathrm{<figure-callout\; id="2"\; label="GT"\; filenames="imgf0001.png"\; state="\{\{state\}\}">GT</figure-callout>}}}{2}$$

All known parameters of the explicit model are known. (The gravitational acceleration g is assumed to be known). If the described parameter identification occurs only once, the resulting Model fixed. However, the measured values can also be recorded and processed during operation. The current parameters obtained in this way can be used to track the model parameters and to adapt to slow changes in the door mechanism, for example due to wear and soiling. In this case, the model is adapted.

As speed generator 4, an asynchronous motor in connection with a frequency converter can be used with an implemented on it, rotor-flux-oriented current control and a superimposed speed control, for example, the torque-forming orthogonal to the rotor flux current component i _sq is used as an internal size.

To generate the torque in a rotary asynchronous motor, it is necessary to generate a magnetic field rotating about the motor axis. A particularly simple description of the relationships between motor current, magnetic flux and motor torque is possible by equations when carrying out a coordinate transformation.

der durch Betrag und den Winkel bezüglich der ersten Motorwicklungsachse gekennzeichnet ist. Die Koordinatentransformation besteht darin, dass man als Bezugspunkt nicht die Position der ersten Wicklungsachse, sondern den aktuellen magnetischen Fluss im Rotor der Maschine wählt. Der Strom im Stator ${\overrightarrow{\mathrm{l}}}_{\mathrm{s}},$

kann dann zerlegt werden in eine zum Rotorfluss parallele Komponente i_sd und eine dazu rechtwinklige Komponente i_sq. Der Betrag des Rotorflusses kann durch die geeignet gesteuerte Stromkomponente i_sd konstant gehalten werden. Es gilt dann Proportionalität zwischen i_sq und dem aufgebrachten Motormoment, so dass i_sq ein Mass für die an der Türkante/Tür wirksame Antriebskraft ist.The stator currents measured in the three motor phases are superimposed to form a resulting current vector ${\overrightarrow{\mathrm{l}}}_{\mathrm{s}}.$

which is characterized by the amount and the angle with respect to the first motor winding axis. The coordinate transformation consists in choosing as reference point not the position of the first winding axis, but the current magnetic flux in the rotor of the machine. The current in the stator ${\overrightarrow{\mathrm{l}}}_{\mathrm{s}}.$

can then be decomposed into a rotor flux parallel component i _sd and a rectangular component i _sq . The amount of rotor flux can be kept constant by the suitably controlled current component i _sd . It then applies proportionality between i _sq and the applied motor torque, so that i _{sq is} a measure of the force acting on the door edge / door driving force.

For example, an asynchronous motor in conjunction with a U / f control implemented thereon can also be used as the speed generator 4, the detected slip serving as a measure of the applied driving force.

$${\mathrm{n}}_{\mathrm{s}}={\mathrm{f}}_{\mathrm{s}}/\mathrm{zp}$$

wobei

s

der Schlupf,

n_s

die Synchrondrehzahl des umlaufenden magnetischen Feldes,

n

die mechanische Drehzahl der Motorwelle,

w_s

die Synchronkreisfrequenz des magnetischen Feldes,

w

die mechanische Kreisfrequenz,

f_s

die aktuelle Synchron- bzw. Ausgangsfrequenz des Frequenzumrichters und

zp

die Polzahl des verwendeten Motors ist.

The slip s is defined according to the following equation: $$\mathrm{s}=\frac{{\mathrm{w}}_{\mathrm{s}}-\mathrm{w}}{{\mathrm{w}}_{\mathrm{s}}}=\frac{{\mathrm{n}}_{\mathrm{s}}-\mathrm{n}}{{\mathrm{n}}_{\mathrm{s}}}$$

$${\mathrm{n}}_{\mathrm{s}}={\mathrm{f}}_{\mathrm{s}}/\mathrm{zp}$$

in which

s

the slip,

n _s

the synchronous speed of the circulating magnetic field,

n

the mechanical speed of the motor shaft,

w _s

the synchronous circuit frequency of the magnetic field,

w

the mechanical angular frequency,

f _s

the current synchronous or output frequency of the frequency converter and

zp

the number of poles of the motor used is.

wobei

M_K

das Kippmoment und

s_K

der Kippschlupf ist.

According to the well-known Kloss formula applies: $${\mathrm{m}}_{\mathrm{M}}=\frac{2{\mathrm{M}}_{\mathrm{K}}}{\mathrm{s}/{\mathrm{s}}_{\mathrm{K}}+{\mathrm{s}}_{\mathrm{K}}/\mathrm{s}}=\frac{2{\mathrm{M}}_{\mathrm{K}}\cdot \mathrm{s}}{{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="imgf0001.png"\; state="\{\{state\}\}">s</figure-callout>}}^2/{\mathrm{S}}_{\mathrm{K}}+{\mathrm{s}}_{\mathrm{K}}}$$

in which

M _K

the tilting moment and

s _K

the tilting slip is.

Both quantities are constant for a given engine and V / f characteristic control.

so dass aus einer gemessenen mechanischen Drehzahl n und der bekannten Frequenz der Ausgangsspannung f_s eines Frequenzumrichters der Schlupf und aus diesem wiederum das Motormoment nach der Formel $${\mathrm{m}}_{\mathrm{M}}=\frac{2{\mathrm{M}}_{\mathrm{K}}}{{\mathrm{s}}_{\mathrm{K}}}\cdot \frac{{\mathrm{f}}_{\mathrm{s}}/\mathrm{zp}-\mathrm{n}}{{\mathrm{f}}_{\mathrm{s}}/\mathrm{z}}$$

berechnet werden kann.For small slip amounts (s <s _K ) the approximation applies: $${\mathrm{m}}_{\mathrm{M}}=\frac{2{\mathrm{M}}_{\mathrm{K}}\cdot \mathrm{s}}{{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="imgf0001.png"\; state="\{\{state\}\}">s</figure-callout>}}^2/{\mathrm{s}}_{\mathrm{K}}+{\mathrm{s}}_{\mathrm{K}}}=\frac{2{\mathrm{M}}_{\mathrm{K}}}{{\mathrm{s}}^2/{\mathrm{S}}_{\mathrm{K}}}\cdot \mathrm{s}$$

so that from a measured mechanical speed n and the known frequency of the output voltage f _{s of} a frequency of the slip and from this in turn the engine torque according to the formula $${\mathrm{m}}_{\mathrm{M}}=\frac{2{\mathrm{M}}_{\mathrm{K}}}{{\mathrm{s}}_{\mathrm{K}}}\cdot \frac{{\mathrm{f}}_{\mathrm{s}}/\mathrm{zp}-\mathrm{n}}{{\mathrm{f}}_{\mathrm{s}}/\mathrm{z}}$$

can be calculated.

As a speed generator, for example, a voltage and frequency controlled asynchronous motor can be used, the measured stator current amount is used as a measure of the driving force.

$$\left|{\mathrm{m}}_{\mathrm{M}}\right|=1/\mathrm{K}\cdot \sqrt{{{\mathrm{l}}_{\mathrm{s}}}^2-{{\mathrm{l}}_{\mathrm{\mu }}}^2}$$

abhängig, wobei·I_rα die im zeitlichen Mittel momentproportionale Stromkomponente, K eine von den Motordaten abhängige Konstante und I_µ der konstante Magnetisierungsstrombetrag ist. Damit ergibt sich der Betrag des Moments aus dem gemessenen Strombetrag nach $${\mathrm{m}}_{\mathrm{M}}=-\mathrm{K}\cdot {\mathrm{l}}_{\mathrm{r\alpha }}$$

$$\left|{\mathrm{m}}_{\mathrm{M}}\right|=1/\mathrm{K}\cdot \sqrt{{{\mathrm{l}}_{\mathrm{s}}}^2-{{\mathrm{l}}_{\mathrm{\mu }}}^2}$$

$$\mathrm{K}=3/2\cdot \mathrm{zp}\cdot \frac{{\mathrm{L}}_{\mathrm{m}}\cdot {\mathrm{U}}_{\mathrm{nom}}}{{\mathrm{L}}_{\mathrm{s}}\cdot 2\mathrm{\pi }\cdot {\mathrm{f}}_{\mathrm{nom}}}$$

$${\mathrm{l}}_{\mathrm{\mu }}=\frac{{\mathrm{U}}_{\mathrm{nom}}}{2\mathrm{\pi }\cdot {\mathrm{f}}_{\mathrm{nom}}\cdot {\mathrm{L}}_{\mathrm{m}}}$$

wobei

zp

die Polpaarzahl,

I_s

der Betrag des Ständerstromes,

L_m

die Hauptinduktivität des Motors,

L_s

die Ständerinduktivität des Motors,

U_nom

die Nennspannung des Motors und

f_nom

die Nennfrequenz des Motors ist.

The time average of the amount of current through the stator winding of the asynchronous machine is in U / f control of the applied motor torque m _M on the formulas $${\mathrm{m}}_{\mathrm{M}}=-\mathrm{K}\cdot {\mathrm{l}}_{\mathrm{r\alpha }}$$

$$\left|{\mathrm{m}}_{\mathrm{M}}\right|=1/\mathrm{K}\cdot \sqrt{{{\mathrm{l}}_{\mathrm{s}}}^2-{{\mathrm{<figure-callout\; id="2"\; label="l\; \mu "\; filenames="imgf0001.png"\; state="\{\{state\}\}">l\; </figure-callout>}}_{\mathrm{\mu }}}^2}$$

depending, wherein · I _rα the _{torque-proportional} in time average current component, K is a dependent of the motor data constant and I _{μ is} the constant magnetizing current. This results in the amount of torque from the measured amount of current $${\mathrm{m}}_{\mathrm{M}}=-\mathrm{K}\cdot {\mathrm{l}}_{\mathrm{r\alpha }}$$

$$\left|{\mathrm{m}}_{\mathrm{M}}\right|=1/\mathrm{K}\cdot \sqrt{{{\mathrm{l}}_{\mathrm{s}}}^2-{{\mathrm{l}}_{\mathrm{\mu }}}^2}$$

$$\mathrm{K}=3/2\cdot \mathrm{zp}\cdot \frac{{\mathrm{L}}_{\mathrm{m}}\cdot {\mathrm{U}}_{\mathrm{nom}}}{{\mathrm{L}}_{\mathrm{s}}\cdot 2\mathrm{\pi }\cdot {\mathrm{f}}_{\mathrm{nom}}}$$

$${\mathrm{l}}_{\mathrm{\mu }}=\frac{{\mathrm{<figure-callout\; id="2"\; label="U\; nom"\; filenames="imgf0001.png"\; state="\{\{state\}\}">U\; </figure-callout>}}_{\mathrm{nom}}}{2\mathrm{\pi }\cdot {\mathrm{f}}_{\mathrm{nom}}\cdot {\mathrm{L}}_{\mathrm{m}}}$$

in which

zp

the pole pair number,

I _s

the amount of the stator current,

L _m

the main inductance of the motor,

L _s

the stator inductance of the motor,

U _nom

the rated voltage of the motor and

f _nom

the rated frequency of the motor is.

Thus, the amount of the drive torque from the measured amount of current can be calculated. Other arrangements and control methods, such as synchronous drives with measurement of the Polradwinkels or Statorstrombetrages or DC drives with stator current measurement, etc., which allow a conclusion on the force actually applied by the actuator are also possible as speed generators.

As a speed generator 4, for example, a synchronous motor can be used.

The limit generator 7 calculates a force limit value from the driving force model value determined by the mathematical model and an allowable disturbance force. In the simplest case, this is done by adding the maximum permissible disturbance force of, for example, 120 N.

As a more sensitive solution for the determination of the force limit, a statistical evaluation method, for example, according to a Gaussian normal distribution can be used. Gaussian normal distribution is only one of many possible distribution functions. Exponential, Weibull or equal distribution can also be used. All these functions have a density function and a distribution function, whereby the calculated numerical values may of course be different. By statistically evaluating the difference between the actual value of the driving force and the value of the driving force provided by the mathematical model, it is possible to determine how well the measured values coincide with the theoretical values when undisturbed. Assuming a Gaussian normal distribution of the difference values can be, as in Fig. 2 from the determined standard deviation, determine how many percent of all difference values exceed a specific limit value exclusively due to random influences without an actual obstacle having occurred in the course of the closing process. Conversely, the minimum limit can be specified and used, where the probability of a wrongly triggered reversing is acceptably small.

Assuming a larger number of measurements, it is found that the difference values scatter around the mean 0 of the density function phi (z) (curve 9) of the normal distribution with a standard deviation of 10 N. According to the distribution function Phi (z) (curve 10) Thus, in the normal distribution, 50% of all difference values are less than 0. 84% of all limit values are less than 10 N, 97.7% are less than 20 N and 99.86% are less than 30 N. If the limit is set to 30 N, then as the door closing force setpoint provided by the mathematical model, only 0.14% of all readings will exceed the threshold by accidental disturbances. Thus, a lower triggering threshold can be achieved without sacrificing reliability and the risk of injury is reduced. On the basis of the current statistical evaluation of the difference values, an adaptation can take place during operation.

Claims (8)

1. Method of force limitation for automatic elevator doors with a door drive comprising a control, motor, and drive mechanism for imparting motion to a car door and a hoistway door according to a pattern of speed and pattern of force corresponding to the position of the door from an open position to a closed position or vice versa, the pattern of force itself being adaptable to door parameters which change with the passage of time, and the doors being stoppable and/or reversible should a disruptive force caused by an obstruction occur while they are in motion, wherein
   the pattern of driving force needed during unobstructed operation is determined by means of a mathematical model for the door drive,
   the mathematical model is based on Newtonian equations of motion for the door mechanism,
   the pattern of driving force requiring to be generated when operating free of disruptive forces is compared with the actual value of the pattern of driving force, and deviations of a specified amount between the necessary pattern of force and the actual value of the pattern of force caused by the disruptive force stop and/or reverse the doors.
2. Method according to Claim 1,
   characterized in that
   the mathematical model is an adaptive model in which the parameters are automatically adjusted to the actual parameters of the door mechanism while the door is in operation.
3. Method according to Claim 1,
   characterized in that
   an asynchronous motor with voltage and frequency control is provided to generate the pattern of force, the measured motor slip serving as a measure of the driving force.
4. Method according to Claim 1,
   characterized in that
   an asynchronous motor with voltage and frequency control is provided to generate the pattern of force, the measured value of the stator current serving as a measure of the driving force.
5. Method according to Claim 1,
   characterized in that
   an asynchronous motor supplied by a frequency converter is provided to generate the pattern of force, the component of current i_sq orthogonal to the rotor flux serving as a measure of the driving force.
6. Method according to Claim 1,
   characterized in that
   a synchronous motor is provided to generate the pattern of force.
7. Method according to Claim 1,
   characterized in that
   a limiting value of force is determined from the model value for the driving force obtained from the mathematical model and a permissible disruptive force, the doors stopping and/or reversing when the limiting value of force is exceeded.
8. Method according to Claim 7,
   characterized in that
   the limiting value of force is determined by means of a method of statistical analysis by reference to a density function and a distribution function.

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