HK1089421B

HK1089421B - An elevator control method and an apparatus for controlling an elevator

Info

Publication number: HK1089421B
Application number: HK06109959.4A
Authority: HK
Inventors: Pekka Jahkonen
Original assignee: 通力股份公司
Priority date: 2003-02-27
Filing date: 2004-02-24
Publication date: 2009-07-10

Description

Elevator control method and apparatus for controlling elevator

Technical Field

The present invention relates to an elevator control method, and an apparatus for controlling an elevator.

Background

In advanced ac elevator drives, the motor is generally controlled by a frequency converter, which is used to adjust the torque and rotational speed of the motor. Each elevator trip may be considered to consist of a departure, an acceleration, a constant velocity part, a deceleration, and a stop at the landing site. The reference speed is typically used to control the motor so that the elevator follows the predetermined speed profile as accurately as possible. An important task in elevator operation is to stop the elevator car just above the landing without sudden speed changes or without moving the car in the opposite direction.

Typically, equal deceleration is used when the elevator is about to stop, and just before stopping, the deceleration is changed at a preselected rate of change, i.e. deceleration rate, in order to achieve the final finishing phase of the speed profile. This method is suitable if the elevator is travelling exactly along the predetermined speed profile.

In the prior art, there are solutions designed to make the elevator walk along the speed curve as precisely as possible until the final deceleration. Such a solution is described, for example, in International patent application No. PCT/FI 97/00265. However, the solution disclosed in this publication is rather complicated and therefore cannot be applied in all elevator drives.

However, when torque control is used in an elevator, it becomes difficult to travel along a reference speed because the torque control determines the total torque of the system. Increasing the gain increases the torque, but this leads to stability problems.

Disclosure of Invention

The object of the invention is to develop a new method of controlling an ac motor used in an elevator, which method is easy to implement and enables the elevator car to be reliably stopped exactly on the ground. To achieve this object, the method of the invention controls the motor by means of the speed adjustment method in the initial deceleration phase and by means of the position adjustment method in the final deceleration phase when the elevator is decelerating, and the moment of transition from the speed adjustment to the position adjustment is mainly determined by means of the elevator speed curve. Similarly, the apparatus of the invention comprises means by which the elevator motor can be controlled in dependence on the position data and means for making a choice whether to control the elevator by reference to speed or by reference to position. Certain other embodiments of the invention have the features disclosed in the dependent claims.

With the solution of the invention, the motor is controlled with a reference position in the final phase before the car stops at the landing site. This will result in an adjustment which is directly dependent on the distance to the desired stop position being both simple and reliable. In the rest of the travel curve, the reference speed is followed, thus taking advantage of the speed adjustment.

According to a preferred embodiment, when the elevator is decelerating, the motor is controlled by the speed adjustment method in the initial stage of deceleration and the motor is controlled by the position and speed adjustment method in the final stage of deceleration, and the moment of transition from speed adjustment to position adjustment is mainly determined by the elevator speed curve. The method of the invention neither affects the normal travel time of the elevator nor makes the control during actual travel more complicated.

According to a second preferred embodiment, the instantaneous value of the speed profile is continuously observed and the motor control method is determined using the instantaneous value of the speed profile.

According to a further preferred embodiment of the method, the remaining distance to the stop position is continuously monitored and the motor control method is determined using this remaining distance.

According to a further embodiment, when the elevator is decelerating, the motor is controlled by a speed adjustment method until a point is reached where the ratio between acceleration and speed is the same as the ratio between remaining distance and speed, and at this point the control is changed to position adjustment. In this way, a control method is achieved that is independent of other driving parameters.

The invention also provides an apparatus for controlling an elevator according to yet another embodiment of the invention, the apparatus comprising means for allowing control of the elevator motor in dependence on position data, and means for making a selection whether to control the elevator by reference to a speed or by reference to a position.

Drawings

The invention will be described in detail hereinafter with reference to embodiments and the accompanying drawings, in which:

FIG. 1 illustrates the final deceleration of the speed profile; and

figure 2 is a diagrammatic representation of a control system implementing the method of the present invention.

Detailed Description

According to fig. 1, in normal operation, the elevator travel curve comprises an initial acceleration, equal acceleration phase, equal velocity phase, equal deceleration phase, and final deceleration. In the deceleration phase, the speed of the elevator or the like decreases with deceleration, which is shown in fig. 1 by V of the speed curve_aAnd (4) partially showing. In the equal deceleration phase, equation v is known₁＝a*t₁Applied to speed, where a is deceleration and t is time, and equation s₁＝1/2*a*t₁ ²Applied to the distance. In other words, when the elevator or the like is gradually stopped at a deceleration, it is at time t₁Internally advance s₁＝1/2*a*t₁ ²The distance of (c). If at the end of the deceleration phase the last completion phase is added to the speed profile, in which case the rate of change of deceleration, i.e. the deceleration rate, is constant, and the value of the deceleration rate is chosen to double the stopping distance, i.e. s₂＝2*s₁＝a*t₁ ²Then the velocity can be solved. For example, if speedThe degree decreases exponentially and at time t 1/c s₁/v₁＝v₁A starts the final completion phase, then the values of speed, deceleration and distance to the landing site simultaneously become zero with great precision. In this case, the following equation can be applied:

v＝v₁*e^-c*t，

d＝1/c*v，

a＝-c*v。

thus, fig. 1 illustrates the definition of the moment at which the transition of the speed adjustment to the position adjustment occurs. The proposed moment is the remaining distance (a)₁+a₂) Equal to the distance a the elevator must travel if the final completion phase is not added₁Twice as much time.

Fig. 2 represents a motor control system implementing the functionality of the present invention. The ratio between the speed and deceleration of the elevator is compared with the ratio between the remaining distance and the speed. When the two ratios are equal, the control is transferred from the equal deceleration phase to the final deceleration, and according to an exponential function v ═ v₁*e^-c*tThe speed is controlled. According to fig. 2, the transition to position adjustment is accomplished by connecting the actual value signal R of the speed controller to the reference position instead of to the reference speed. The reference position is some function of the distance to the landing site measured by the position feedback device.

The above description should not be taken as limiting the scope of patent protection; instead, the embodiments of the invention may be freely varied within the limits defined in the claims.

Claims

1. An elevator control method, in which an elevator motor is controlled in such a way that the speed of the elevator follows a reference speed, and in the initial deceleration phase the motor is controlled by means of a speed adjustment method, and in the final deceleration phase the motor is controlled by means of a position-speed adjustment method, when the elevator is decelerating, characterized in that the moment of transition from speed adjustment to position adjustment is mainly determined by means of the elevator speed curve.

2. Method according to claim 1, characterized in that the instantaneous value of the speed profile is continuously monitored and the motor control method is determined using the instantaneous value of the speed profile.

3. Method according to claim 1 or 2, characterized in that the remaining distance to the stop position is continuously monitored and the motor control method is determined using this remaining distance.

4. A method according to claim 1 or 2, characterized in that when the elevator is decelerating, the motor is controlled by a speed adjustment method until a point is reached where the ratio between acceleration and speed is the same as the ratio between remaining distance and speed, and at this point the control is changed to position adjustment.

5. A method according to claim 3, characterized in that when the elevator is decelerating, the motor is controlled by the speed adjustment method until a point is reached where the ratio between acceleration and speed is the same as the ratio between remaining distance and speed, and at this point the control is changed to position adjustment.

6. An arrangement for controlling an elevator, said arrangement comprising means for allowing control of an elevator motor in dependence on a reference position or a reference speed, characterized in that the arrangement comprises means for determining the moment of transition so as to select the control of the elevator motor from the reference speed to the reference position.