Method for determining moving mass of a door system

Abstract

A method for determining moving mass of a door system, actuated by a motor, wherein a) the motor electrical output, which is converted into mechanical output, is measured, b) the electrical output is summed during opening and/or closure, starting from the beginning of the actuation of the mass by the motor from initial rest until an end rest position is reached following completion of the actuation to determine energy losses, c) measurement of the maximum speed of the mass of the door system is measured during opening and/or closure, d) the electrical output provided by the motor from the initial rest position of the mass of the door system until achieving the maximum speed v thereof is summed, and the obtained energy value is reduced by the energy losses occurring up to this time point to determine the mass of the door system from the obtained kinetic energy.

Claims

1. A method for determining a moving mass m of an elevator door system driven by a motor to automatically compensate for at least one of frictional forces and closing forces associated with the door system, the method comprising: a) measuring an electrical power of the motor which is converted into mechanical power; b) summing the electrical power for at least one of (i) an intended opening and (ii) intended closing movement of the door system from a start of driving the mass m by the motor from an initial rest position until a final rest position is reached upon termination of driving to determine energy losses; c) measuring a maximum speed of the mass of the door system during at least one of the (i) intended opening and (ii) the intended closing movement of the door system; and d) attaining and summing the electrical power provided by the motor from the initial rest position of the mass m of the door system to a point in time at which the maximum speed of the door system is attained and reducing an obtained energy value by energy losses that have occurred up to this point in time to determine the mass m of the door system from an obtained kinetic energy E to automatically compensate for at least one of the frictional forces and closing forces associated with the door system; wherein the mass of the door system is determined in accordance with the following relationship: $m=\frac{2E}{v^2}.$

2. The method of claim 1, wherein the energy losses are due to at least one of the frictional forces and the closing forces.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The FIGURE is a flowchart of the method in accordance with the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

(2) In accordance with the invention, the method involves permanent summing of the electrical power P.sub.el supplied to and consumed by the motor. This enables an energy balance to be drawn at any points in time. By skillfully selecting these instants, the door mass can be determined with automatic compensation of friction and closing forces. In addition, by concatenation of opening and closing movement, the friction and any possible closing force (e.g., due to a spring or a counterweight) can be explicitly calculated.

(3) For determining the mass, the door system is regarded as an energy store, as only the mass m is suitable for storing and delivering energy again during a movement. All the other forces only remove energy from the door system and do not return it again during an opening or closing movement. As the door has the same energy state at the start and at the end (the door is stationary), the resulting energy corresponds to the losses due to friction or rather overcoming the spring force or counterweight. The measured energy summed at the instant of maximum speed v during the movement, i.e., the time integral of the power P.sub.el electrically delivered hitherto, corresponds to the present energy sum of the kinetic energy of the mass m and the hitherto required friction and counterweight energy. As the kinetic and friction energy at the end of the movement is known, this can be taken into account pro rata for the intermediate value with maximum speed, directly yielding the kinetic energy within the system. This energy value corresponds to the known relationship:

(4) $\begin{array}{cc}E=\frac{1}{2}.Math.m.Math.v^2,& \mathrm{Eq}.1\end{array}$
so that the door mass m can be immediately calculated according to

(5) $\begin{array}{cc}m=\frac{2E}{v^2}.& \mathrm{Eq}.2\end{array}$

(6) In order to determine the electrical energy, in contrast to the conventional above-described method, instead of the voltage-time surface, the back-EMF U.sub.EMK is directly used that results very simply from the current and easily measurable speed v.sub.Mot via a proportionality factor k.sub.v. The electrical power P.sub.el that is converted into mechanical power is obtained from the following relationship:
P.sub.el=U.sub.EMK.Math.I.sub.MotEq. 3
(motor current: I.sub.Mot).

(7) Due to the relationship
U.sub.EMK=k.Math..sub.MotEq. 4

(8) The factor k.sub.v results from the ratio of the nominal voltage U.sub.nom to the idling speed v.sub.Mot.sub._.sub.LL, i.e., no-load condition, in accordance with the relationship:

(9) $\begin{array}{cc}{k}_v=\frac{U_{\mathrm{nom}}}{v_{\mathrm{Mot\_LL}}}& \mathrm{Eq}.5\end{array}$
the electrical power can now also be determined via the speed:
P.sub.el=k.sub..Math..sub.Mot.Math.I.sub.MotEq. 6

(10) The product of current I.sub.Mot and speed v.sub.Mot multiplied by a motor constant k.sub.v directly yields the electrical power P.sub.el that is converted into mechanical power. The time consuming and error prone compensation of internal resistance, dead time and fluctuating DC-link voltage can thus be eliminated.

(11) In accordance with the method of the invention, the door system is set in motion for the opening or closing process by a motor via a drive belt. The motor current i.sub.q and rotor position .sub.mot are cyclically measured (e.g., in interrupt mode). Although acyclic measurement is also conceivable, the time interval must then likewise be determined.

(12) The rotor speed .sub.mot can be determined from the rotor position .sub.mot by differentiation.

(13) For calculating the energy per cycle, two approaches can be taken: a) Via current i.sub.q, speed .sub.mot and cycle time t
E=k.sub.E.Math.i.sub.q.Math..sub.mot.Math.t (Note: t denotes the cycle time) b) Via current i.sub.q and rotor position .sub.mot:
E=k.sub.t.Math.i.sub.q.Math..sub.mot (Note: .sub.mot denotes the change in the rotor angle in the last cycle t).

(14) The above relationships can be very easily transformed into one another and offer comparable accuracy:

(15) With

(16) $=\frac{{}_{\mathrm{mot}}}{t}\mathrm{and}$$k_E=k_t=\frac{U}{}=\frac{M}{i_q},$
the second relationship can be derived directly from the first. Here, U denotes the back-EMF and M the torque. k.sub.E and k.sub.t are constants.

(17) For better understanding of the energy relationships, the entire system can be regarded as an interconnection of two lossless energy stores (toothed belt and door mass), where all the energy losses are attributed to friction.

(18) The mass determination sequence comprises the following steps: a) Measurement of the motor current i.sub.q. In the case of DC drives, this is the motor current itself, while for AC drives it is the torque-generating current i.sub.q. b) Measurement of the rotor position .sub.mot. Different measurements can be obtained depending on the sensor used; the important thing is conversion to the angle in radians (2) and taking the difference with respect to the last position. c) Calculation of the product i.sub.q.Math..sub.mot and summation The product of motor current i.sub.q and change in rotor position .sub.mot is proportional to the energy in the cycle. This value is summed and subsequently multiplied by the constant k.sub.t. d) Summation of the angle rotated through .sub.mot,sum. In parallel with this summation, the distance traveled by the rotor is also summed (summing of the angle). e) Storing of intermediate values. For subsequent calculation of the mass m and the friction, the intermediate results obtained at the instant of maximum door energy, and the total values for opening and closing process, are stored. Also stored are: the respective rpm .sub.mot, the product sum

(19) $\frac{E_{\mathrm{mot},\mathrm{sum}}}{k_t}=.Math.\left(i_q.Math.{}_{\mathrm{mot}}\right)$
and the rotor angle sum .sub.mot,sum=.sub.mot. f) Storage of end values. In addition to the intermediate results in the opening and closing direction, the product and angle sums for the complete opening and closing movement are stored. By definition, the rpm is zero at the end points. g) Calculation of the friction. The average friction for the opening and the closing movement is calculated. The lossless energy stores of the overall system again possess identical values at the end positions. Intermediate charges have been equalized again. The energy remaining in the system therefore corresponds precisely to the frictional losses. Total energy from the product sum:

(20) $E_{\mathrm{frict},\mathrm{ges}}=k_t.Math.\underset{=0}{\overset{=\mathrm{Endpos}}{.Math.}}\left(i_q.Math.{}_{\mathrm{mot}}\right)$ The friction torque results from the total energy and the rotor angle covered:

(21) $M_{\mathrm{frict}}=\frac{E_{\mathrm{frict}}}{{}_{\mathrm{mot},\mathrm{sum}}}$ h) Calculation of the door mass m. From the product sum stored at the instant of maximum door speed, the energy supplied hitherto can be calculated:

(22) $E_{\mathrm{sum},\mathrm{zw}}=k_t.Math.\underset{=0}{\overset{=\mathrm{Zwischenwet}}{.Math.}}\left(i_q.Math.{}_{\mathrm{mot}}\right).$

(23) Some of this energy was required for overcoming the friction. This energy portion E.sub.frict,ges is calculated via the friction torque and the ratio of partial distance .sub.mot,zw to total distance .sub.mot,sum:

(24) 0$E_{\mathrm{frict},\mathrm{zw}}=M_{\mathrm{frict}}.Math.{}_{\mathrm{mot},\mathrm{zw}}=\frac{{}_{\mathrm{mot},\mathrm{zw}}}{{}_{\mathrm{mot},\mathrm{sum}}}.Math.E_{\mathrm{frict},\mathrm{ges}}.$

(25) The kinetic energy E.sub.door,kin is obtained as the difference between energy supplied E.sub.sum,zw and energy lost due to friction E.sub.frict,zw:

(26) $E_{\mathrm{door},\mathrm{kin}}=E_{\mathrm{sum},\mathrm{zw}}-E_{\mathrm{frict},\mathrm{zw}}=E_{\mathrm{sum},\mathrm{zw}}-\frac{{}_{\mathrm{mot},\mathrm{zw}}}{{}_{\mathrm{mot},\mathrm{sum}}}.Math.E_{\mathrm{frict},\mathrm{ges}}$

(27) Door mass m:

(28) $m=\frac{2.Math.E_{\mathrm{door},\mathrm{kin}}}{{\left({}_{\mathrm{mot}}.Math.r\right)}^2}$
(Radius r of the drive shaft for the toothed belt).

(29) In accordance with the disclosed method, after the last equation the mass m of the door system is determined based in each case on an intended opening and/or closing movement. Accordingly, an intended single movement, opening or closing movement, suffices, but the to-be-determined mass m of the door system can also be determined as an average of the results of the two movements. Intended opening and closing movements are defined as opening and closing movements that are not different from opening and closing movements during intended, i.e., normal use. Markedly different frictional torques during opening and closing indicate an additional system force (e.g., a counterweight or a spring) and/or the efficiency could be direction-dependent. The toothed belt energy store postulated in the system must contain approximately the same energy at all measuring points (at the start, for the intermediate value and at the end position) (or rather the differences must be small compared to the total energy), as otherwise accuracy will suffer. The method it accordance with the invention can be applied using virtually any running curves. It is merely necessary to ensure that the kinetic energy of the door can be sufficiently clearly differentiated from the frictional energy, as otherwise accuracy will suffer. The method in accordance with the invention automatically also yields the friction, which is of interest for servicing purposes. The method in accordance with the invention is relatively robust and provides good repeatability, as it operates in an integrated manner and averages out superimposed noise. Instead of evaluating the actual speed for the intermediate value, the target speed or a combination of the two could be used.

(30) The FIGURE is a flowchart of the method in accordance with the invention. The method comprises measuring an electrical power P.sub.el of the motor which is converted into mechanical power, as indicated in step 410. Next, the electrical power P.sub.el for at least one of (i) an intended opening and (ii) intended closing movement of the door system from a start of driving the mass m by the motor from an initial rest position until a final rest position is reached upon termination of driving is summed to determine energy losses, as indicated in step 420.

(31) Next, a maximum speed v of the mass of the door system is measured during at least one of the (i) intended opening and (ii) the intended closing movement of the door system, as indicated in step 430.

(32) The electrical power provided by the motor from the initial rest position of the mass m of the door system to the point at a time when the maximum speed v of the door is attained reducing an obtained energy value by energy losses that have occurred up to this point in time is now attained and summed to determine the mass m of the door system from an obtained kinetic energy E in accordance with the following relationship:

(33) $m=\frac{2E}{v^2},$
as indicated in step 440.

(34) While there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the method described and illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.