WO2009019322A1

WO2009019322A1 - Control of the motion of a transport appliance

Info

Publication number: WO2009019322A1
Application number: PCT/FI2008/000092
Authority: WO
Inventors: Pekka Jahkonen
Original assignee: Kone Corporation
Priority date: 2007-08-09
Filing date: 2008-08-05
Publication date: 2009-02-12
Also published as: FI20070601A0; FI119507B

Abstract

The invention relates to a method and an appliance for controlling the motion of a transport appliance (18, 19, 20) incorporated in a transport system (7). In the method at least a first reference of motion during acceleration or deceleration of the transport appliance is defined by means of a sine function. The transport system (7) comprises a motion control (4), which is fitted to form one or more references (8, 9, 10, 11, 14, 15, 16, 17) for controlling the motion.

Description

CONTROL OF THE MOTION OF A TRANSPORT APPLIANCE Field of the invention

The object of the invention is a method as defined in the preamble of claim 1 and an arrangement as defined in the preamble of claim 8 for controlling the motion of a transport appliance.

Prior art

In transport systems, such as in elevator systems, determination of the speed of the elevator car is normally performed by means of a speed reference. Three parts of a speed reference can be distinguished: acceleration, even speed and deceleration. Acceleration and deceleration can again be divided into three parts: the starting part of acceleration, where the acceleration is increased until the phase of even acceleration is reached. At the end of even acceleration the acceleration is reduced until the phase of even speed is reached. During deceleration the acceleration term, of course, changes into deceleration.

The speed reference is normally formed from the derivative of the acceleration reference of the transport appliance when starting, i.e. the jerk reference. The acceleration reference, and from this further the speed reference, is integrated from the jerk reference. The jerk reference is often a square wave in shape. The jerk reference, acceleration reference and speed reference are normally continuous piecewise functions, for each of which is a dedicated equation in the different phases of the speed reference. The reconciliation of these functions so that the speed reference is even in shape and so that the switching of the control of the transport appliance from the speed reference phase to another occurs at the right time and position conventionally requires numerous long groups of equations that involve laborious calculations. These run-time calculations demand substantial computing capacity. Purpose of the invention

The purpose of the invention is to disclose a method and an arrangement for controlling the motion of a transport appliance. More particularly, the purpose of the invention is to disclose a determination of the references of the motion of a transport appliance that is simpler and more versatile than prior art. As presented in the invention the different references of the motion of the transport appliance can be defined for use by the motion control using only minimal computing power, while at the same tame taking into account the requirements set by the control of the transport appliance as well as by the mechanics of the transport appliance.

Characteristic features of the invention

The method according to the invention for controlling the motion of a transport appliance is characterized by what is disclosed in the characterization part of claim 1. The arrangement according to the invention for controlling the motion of a transport appliance is characterized by what is disclosed in the characterization part of claim 8. Other features of the invention are characterized by what is disclosed in the other claims. Some inventive embodiments are also discussed in the descriptive section of the present application. The inventive content of the application can also be defined differently than in the claims presented below. The inventive content may also consist of several separate inventions, especially if the invention is considered in the light of expressions or implicit sub-tasks or from the point of view of advantages or categories of advantages achieved. In this case, some of the attributes contained in the claims below may be superfluous from the point of view of separate inventive concepts.

In the method according to the invention for controlling the motion of a transport appliance incorporated in a transport system the transport system comprises a motion control, in which one or more references are formed for controlling the motion. According to the invention at least a first reference of motion during acceleration or deceleration of the transport appliance is defined by means of a sine function. Motion control refers to the devices and algorithms with which the output of the motor moving the transport appliance are set for moving the transport appliance according to the reference value of the motion. Sine function refers to a function that is based on a sine function or on a cosine function.

In one method according to the invention the transport appliance is fitted to move in a set movement area, according to the aforementioned reference of the motion of the transport appliance.

In one method according to the invention the motion of the transport appliance is controlled during acceleration or deceleration as a response to the aforementioned first reference of motion of the transport appliance.

In one method according to the invention the reference is preferably formed from a plurality of consecutive reference values or can be described as a continuous reference curve in relation to time.

In one method according to the invention at least one of the following references of motion of the transport appliance is directly or indirectly derived from the first reference of motion of the transport appliance:

the reference of the jerk s'" of the transport appliance

the reference of the acceleration s" of the transport appliance

the reference of the speed s' of the transport appliance

the reference of the maximum permitted limit value of motion of the transport appliance the reference of the minimum permitted limit value of motion of the transport appliance

the reference of the acceleration distance s1 of the transport appliance

- the reference of the deceleration distance s2 of the transport appliance

the reference of the motion during a fast stop of the transport appliance

When the reference is based directly on the first reference of motion of the transport appliance, the reference is derived from this first reference. When the reference is based indirectly on the first reference of motion of the transport appliance, the reference is derived from an other than the first reference of motion. The maximum permitted limit value of motion of the transport appliance refers to the absolute value of the maximum permitted limit value, correspondingly the minimum permitted limit value refers to the absolute value of the minimum permitted limit value

In one method according to the invention the reference of the jerk s'" of the transport appliance is defined by means of a sine function.

In one method according to the invention the position data X1 of at least one sensor indicating the stopping location of the transport appliance is tabled in memory, the position X of the transport appliance is measured, the distance E of the transport appliance to the stopping location X1 is defined by comparing the position X of the transport appliance to the tabled stopping location X1 of the transport appliance and also the distance of the transport appliance to the stopping location E is compared to the reference of the deceleration distance s2 of the transport appliance. When the distance of the transport appliance to the stopping location E has decreased to the magnitude of the reference value s2 of the deceleration distance of the transport appliance, deceleration of the transport appliance is started. The transport appliance can execute a learning run, during which the transport appliance reads the sensors indicating the stopping location and records the aforementioned position data of the sensors in memory. Position data can also, of course, be supplied to the transport appliance manually.

The position X of the transport appliance can be measured e.g. by means of an encoder or tachometer fitted to the shaft or the traction sheave of the motor of the transport appliance. If the motor of the transport appliance is a synchronous machine, it is possible to measure the position of the transport appliance also by means of e.g. the frequency of the voltage reference or current reference of the motor. For example, in an elevator system the pulley of the overspeed governor, to which for instance an encoder could be fitted, would also be a possible measuring location of the speed of the elevator car. The distance E of the transport appliance to the stopping location can be determined by means of a comparison of the stopping location X1 and the position X of the transport appliance e.g. with the equation:

E = X_x -X

In one method according to the invention the motion of the transport appliance is measured and the measured value of motion of the transport appliance is compared to the aforementioned maximum permitted limit value of motion of the transport appliance and possibly also to the aforementioned minimum permitted limit value of motion of the transport appliance. When the measured value of motion of the transport appliance deviates outside the range defined by the limit values of permitted motion, the emergency stop is activated.

In one method according to the invention the mechanical vibration frequency of the transport appliance is determined and the frequency and possibly also the harmonic of the frequency of the sine function used in the definition of the aforementioned reference of the motion of the transport appliance is fitted to differ from the mechanical vibration frequency of the transport appliance.

In the arrangement according to the invention for controlling the motion of a transport appliance incorporated in a transport system the transport system comprises a motion control, which is fitted to form one or more references for controlling the motion. At least a first reference of motion during acceleration or deceleration of the transport appliance is defined by means of a sine function.

In one embodiment of the invention the motion control is fitted to control the motion of the transport appliance during acceleration or deceleration as a response to the aforementioned first reference of motion of the transport appliance.

In one embodiment of the invention the reference of motion during acceleration or deceleration of the transport appliance is defined by means of at least a first and a second sine function. The frequencies and/or phases of the aforementioned first and second sine function are fitted to differ from each other.

In one embodiment of the invention the frequencies of the aforementioned first and second sine function and possibly also the harmonics of the frequency are fitted to differ from the mechanical vibration frequency of the transport appliance.

In one arrangement according to the invention the aforementioned reference is preferably formed from a plurality of consecutive reference values or can be described as a continuous reference curve in relation to time.

One motion control according to the invention comprises means for deriving some reference of motion of the transport appliance from the aforementioned first reference of motion of the transport appliance. One arrangement according to the invention comprises a measurement of motion, and the transport appliance is fitted to compare one or more measured values of motion of the transport appliance to the maximum permitted limit value of motion of the transport appliance and possibly also to the minimum permitted limit value of motion of the transport appliance. In this case when the measured value deviates outside the range defined by the limit values of permitted motion, the transport appliance is fitted to activate the emergency stop.

One arrangement according to the invention comprises determination of the mechanical vibration frequency of the transport appliance. The motion control is in this case fitted to select the frequency of the aforementioned sine function and possibly also the harmonics of the frequency to deviate from the determined mechanical vibration frequency of the transport appliance.

The transport appliance of the transport system according to the invention refers here generally to a transport appliance intended for moving people or goods. These kinds of transport systems are, for instance, an elevator system, an escalator system, a travelator system and a crane system. The invention is suited for use also in e.g. the control of trains or, for instance, in the control of various conveyors such as conveyor belts of power plants, factories or warehouses.

Advantages of the invention

With the invention at least one of the following advantages is achieved:

- When some reference of the motion of the transport appliance is defined by means of a sine function, calculation of the reference is simplified. More particularly it is possible to implement the calculation with a so- called MAC (multiply-accumulate) unit, which type of unit is contained in modern DSP (digital signal processor) processors or e.g. in programmable logic circuits. Simplifying the calculation makes it possible for the control of motion of the transport appliance to be implemented with one processor or similar controller. On the other hand it is possible to duplicate the control as parallel control of two processors, in which case both processors can independently calculate the reference of motion of the transport appliance. In this case processors operating in parallel can supervise the operation of each other and the safety of the transport system improves.

- The other references of motion of the transport appliance can be derived from the first reference with a minor additional calculation, e.g. using the aforementioned MAC units or similar computing units. Additionally it is possible to freely derive the references of motion with a minor additional calculation from the first reference such that e.g. it is possible to form either the reference of jerk or alternatively the reference of speed from e.g. the reference of acceleration, in which case the calculation is more versatile than in those prior-art formations of a reference value of motion in which essentially the reference value of jerk is first formed and on the basis of this the reference values of acceleration and of speed are derived.

- When the transport appliance is controlled according to a reference of motion, possible vibration of the transport appliance occurs at the excitation frequencies determined by the reference of motion. When the references of motion are defined on the basis of a sine function, also the possible excitation frequencies of the transport appliance are determined from the frequency of the sine function and to some extent also from the harmonics of this frequency. In this case it is possible to select the frequency of the sine function such that the frequency and possibly also the harmonics of the frequency deviate from the possible resonance frequencies of the transport appliance, in which case a run with the transport appliance is more even and the dissipated energy caused by mechanical vibration as well as the wear of the appliance decrease. - It is also possible at any time whatsoever during a run of the transport appliance to derive some second reference of motion, in which case the transport appliance is able to react quickly to the changes of the control. For example, during acceleration of the transport appliance it is possible to define the reference s2 of the distance to be traveled during deceleration of the transport appliance, and as the distance of the transport appliance from the stopping location E decreases to the magnitude of the reference value s2 of the distance to be traveled during deceleration of the transport appliance it is possible to interrupt acceleration and switch to decelerating the transport appliance.

- It is possible to change the acceleration or deceleration of the transport appliance easily in the middle of a run, for instance, according to the operating mode of the transport appliance. If for example a problem is detected in the run-time operation of the transport appliance, by increasing the frequency of the sine function it is possible to increase the deceleration of the transport appliance and to drive the transport appliance to a stop with a fast stop at a shorter stopping distance than the normal stop.

- It is also possible to derive the permitted extreme values of motion of the transport appliance during a run from the reference of the motion of the transport appliance and it is possible to stop the transport appliance with an emergency stop when the measured motion of the transport appliance deviates from these extreme values. An emergency stop can be executed e.g. by controlling the mechanical brake of the transport appliance, or the control of the transport appliance can also execute a fast stop.

- The moving capacity of the transport appliance can also, if necessary, easily be changed, for instance on the basis of monitoring the traffic of the transport appliance, in which case e.g. it is possible in the middle of a run, or between runs, to increase or to decrease the acceleration of the transport appliance by changing some aforementioned reference of motion setting the frequency of the sine function, and it is also possible to derive re-updated references directly or indirectly from the changed references of motion for the purpose of monitoring traffic.

Presentation of drawings

Fig. 1 presents an elevator system according to the invention

Fig. 2 presents the references of the motion of the elevator car.

Fig. 3 presents the references of the motion of the elevator car.

Embodiments

Fig. 1 presents an elevator system 7 according to the invention. Figs. 2 and 3 present references of motion of the elevator car, according to which the motion control 4 endeavors to place the elevator car 20 in the elevator shaft. Fig. 2 presents the references of motion of the elevator car during acceleration 12 as well as during deceleration 13.

The elevator car 20 and the counterweight 19 are moved in the elevator shaft with the elevator motor 3 via ropes. The power supply of the elevator motor 3 occurs from a network supply 1 through a frequency converter 2. The frequency converter 2 operates the motor 3 with the motion control 4. The motion control 4 sends to the frequency converter 2 the torque reference of the motor 3, with which the motion control endeavors to set the measured speed of the motor 3 according to the reference 10 of speed. The motion control 4 measures the speed of the motor 3 from the measuring signal 6 of the tachometer 5 fitted to the traction sheave so as to be friction-operated. The tachometer 5 can also be fitted to the shaft of the motor 3, in which case the accuracy of the measuring signal 6 improves, especially in measuring position.

Before using the elevator for the first time a learning run is driven in the elevator shaft with the elevator car 20, in which case the elevator car is sent to drive upwards from the magnetic switch 21 indicating the position of the bottommost floor. The magnetic switch 21 of the bottommost floor sets a reference point for the position measurement of the elevator car, and the motion control 4 starts to update the changing position data of the elevator car in relation to the reference point by integration from the measuring signal 6 of the speed of the elevator car. When the elevator car arrives from below at the magnetic switch 21 of a new floor, the floor position data is recorded in a floor table. The elevator car thus drives through the elevator shaft and records the positions of the floors.

In normal operation of the elevator the motion control sets the position of the elevator car during a run by integration from the measuring signal 6 of the speed of the motor, compares the measured position data to the position data of the destination floor in the floor table and calculates the distance E to the destination floor 22 determined by these position data. Simultaneously the motion controller sets the reference 11 of the deceleration distance s2. As the distance to the destination floor 22 decreases to the magnitude of the deceleration distance s2, the motion control starts deceleration of the elevator car.

The motion control 4 can also read the measuring signals of a sensor indicating motion of the elevator car 20 and compare these to each other to verify the integrity of the measurements. The motion control can e.g. read the measuring signal of the sensor that is fitted to the pulley of the overspeed governor (not shown in figure) and that measures motion of the elevator car via the rope of the overspeed governor, in addition to the measuring signal 6 of the tachometer 5 fitted to the traction sheave or the shaft of the motor 3, in which case the motion control can make deductions about e.g. slipping of the ropes of the elevator car on the traction sheave by comparing the measurements of speed.

The motion controller compares the measured speed 6 to the maximum permitted limit value 14 of speed of the elevator car and also to the minimum permitted limit value 15. When the measured value 6 of speed deviates outside the range defined by the limit values 14, 15 of permitted motion, the motion control 4 activates the emergency stop. The motion control 4 can also execute different emergency stops according to the severity of the problem detected. If the elevator car 20 is situated in the middle of the elevator shaft, the motion control 4 can execute a fast stop by setting an early reference 17 of speed, in which case the deceleration is greater than during normal deceleration. This occurs by increasing the frequency of the sine function used in the definition of the reference 10 of speed s'. On the other hand the motion control 4 can also control the machinery brake that prevents motion of the elevator motor 3. When the elevator car 20 is situated at a pre-defined distance closer to the end of the elevator shaft than the limit value, the motion control 4 can control, in addition to the control of the machinery brake, the separate car brake to engage the guide rail of the elevator car.

The motion control endeavors to set the reference 8 of the jerk s'" of the elevator car 20, the reference 9 of the acceleration s" and also the reference 10 of the speed s' such that the excitation frequencies and possibly also the multiples, i.e. the harmonics, of the frequency differ from the resonance frequency of the elevator system. The elevator car 20, the counterweight 19 and the elevator roping 18 form a mechanical oscillator, which has a certain natural frequency. The natural frequency of this oscillator, i.e. the resonance frequency, can be determined by calculation on the basis of the mechanical properties of materials, or it can also be measured e.g. by giving a step-like torque excitation with the elevator motor 3 and measuring the motion response of the elevator car 20 or of the counterweight 19. The natural frequency of the vibration can also be determined by driving the elevator with the frequency converter 2, by summing the noise into, for instance, the speed reference 10 of the elevator car and by measuring the spectrum of the measuring signal 6 of the speed of the motor 3.

Since the references 8, 9, 10, 11 , 14, 15, 16, 17 of motion during acceleration and deceleration are derived directly or indirectly from some other reference of motion defined by means of a sine function, determination of the excitation frequency of the references of motion occurs by determining the frequency of the aforementioned sine function.

If the equation of the reference 8 of the jerk s'" during acceleration is defined by means of a sine function, the parameters of which sine function are the amplitude y of the reference value of jerk, the excitation frequency fj and the time t, the descriptor can be presented, for instance, in the form:

s'"= y*sm(2π*f_j *ή

The time t is here set to start from zero at the starting moment of acceleration. Correspondingly, if the time t is defined to start from zero at the start of deceleration, for the reference of jerk during deceleration the equation derived can be:

s"^r= -y*sin(2π*f; *t)

If the initial value of the acceleration and deceleration of the elevator car is zero, and the time t is defined to start from zero at the start of acceleration and deceleration, the reference 9 of the acceleration s" of the elevator car can in this case be defined during acceleration by means of a sine function as follows:

*"= -^—(l-cos(2^ */;. *;)) and during deceleration as follows:

$"= - — (l - cos(2τr * / * t))

2π* f_; ^{V J l })}

The reference 10 of the speed s' of the elevator car during acceleration can be defined by means of a sine function, for instance, as follows:

j'= ^y *t —_t — ^—ΓΓ- *sin(2^r *f_t *t)

When the time t is defined to start from zero at the start of deceleration and the reference value of even speed of the elevator car is marked as s'_o, the reference 10 of speed s' during acceleration can be defined by means of a sine function, for instance, as follows:

s'= s\ — *t + -. — ^—~-* sm(2π* f_! *t)

In this elevator system the greatest run speed of the elevator car is 1 m/s, the greatest acceleration and also deceleration is 1m/s² and deceleration distance is 1 meter. In this case the reference 10 of the speed s' during acceleration is obtained from the aforementioned descriptor:

π *t -*sin(π *t) s'= * '-

2π

In this case the elevator car achieves an even speed in 2 seconds, the average value of the acceleration of the elevator car is 0.63 m/s² and the average value of jerk is 1 m/s³. The excitation frequency ή of the reference of speed is in this case 0.5 Hz. The mechanical vibration frequency of the elevator is appreciably higher than this, between 2...5Hz, in which case the excitation frequency fj of the reference of speed probably does not produce vibration in the elevator. The invention is described above by the aid of a few examples of its embodiment. It is obvious to the person skilled in the art that the invention is not limited to the embodiments described above, but that many other applications are possible within the scope of the inventive concept defined by the claims presented below.

Claims

1. Method for controlling the motion of a transport appliance (18, 19, 20) incorporated in a transport system (7), wherein the transport system comprises a motion control (4), in which one or more references (8, 9, 10, 1 1 , 14, 15, 16, 17) for controlling motion are formed, and in which the transport appliance is fitted to move in a set movement range (22) according to the aforementioned reference of motion of the transport appliance, characterized in that:

- in the method at least a first reference (8, 9, 10, 1 1 , 14, 15, 16, 17) of motion during acceleration or deceleration of the transport appliance is defined by means of a sine function

- the motion of the transport appliance is controlled during acceleration or deceleration as a response to the aforementioned first reference of motion of the transport appliance.

2. Method according to claim 1 , characterized in that the reference is preferably formed from a plurality of consecutive reference values or can be described as a continuous reference curve in relation to time.

3. Method according to claim 1 or 2, characterized in that:

At least one of the following references of motion of the transport appliance is directly or indirectly derived from the first reference of motion of the transport appliance:

- the reference (8) of the jerk s'" of the transport appliance

- the reference (9) of the acceleration s" of the transport appliance - the reference (10) of the speed s' of the transport appliance

- the reference (14) of the maximum permitted limit value of motion of the transport appliance

- the reference (15) of the minimum permitted limit value of motion of the transport appliance

- the reference (16) of the acceleration distance s1 of the transport appliance

- the reference (11 ) of the deceleration distance s2 of the transport appliance

- the reference (17) of the motion during a fast stop of the transport appliance

4. Method according to any of the preceding claims, characterized in that:

- the reference (8) of the jerk s'" of the transport appliance is defined by means of a sine function

5. Method according to any of the preceding claims, characterized in that:

- at least one position data X1 of the sensor (21 ) indicating the stopping location of the transport appliance is tabled in the memory of the control

- the position X of the transport appliance is measured

- the distance E (22) of the transport appliance to the stopping location X1 is defined by comparing the position X of the transport appliance to the tabled stopping location X1 of the transport appliance

- the distance of the transport appliance to the stopping location E (22) is compared to the reference (11) of the deceleration distance s2 of the transport appliance

- when the distance of the transport appliance to the stopping location E (22) has decreased to the magnitude of the reference value s2 of the deceleration distance of the transport appliance, deceleration of the transport appliance is started

6. Method according to any of the preceding claims, characterized in that

- the motion of the transport appliance is measured

- the measured value (6) of motion of the transport appliance is compared to the aforementioned maximum permitted limit value (14) of motion of the transport appliance and possibly also to the aforementioned minimum permitted limit value (15) of motion of the transport appliance

- when the measured value (6) of motion of the transport appliance deviates outside the range defined by the limit values (14, 15) of permitted motion, the fast stop is activated

7. Method according to any of the preceding claims, characterized in that:

- the mechanical vibration frequency of the transport appliance (18, 19, 20) is determined

- the frequency and possibly also the harmonic of the frequency of the sine function used in the definition of the aforementioned reference (8, 9, 10, 11 , 14, 15, 16, 17) of the motion of the transport appliance is fitted to differ from the mechanical vibration frequency of the transport appliance

8. Arrangement for controlling the motion of a transport appliance (18, 19, 20) incorporated in a transport system (7), wherein the transport system comprises a motion control (4), which is fitted to form one or more references (8, 9, 10, 11 , 14, 15, 16, 17) for controlling motion, and which transport appliance is fitted to move in a set motion range (22) according to the aforementioned reference of motion of the transport appliance, characterized in that at least a first reference (8,

9, 10, 1 1 , 14, 15, 16, 17) of motion during acceleration or deceleration of the transport appliance is defined by means of a sine function, and in that the motion control (4) is fitted to control motion of the transport appliance during acceleration or deceleration as a response to the aforementioned first reference of motion of the transport appliance.

9. Arrangement according to claim 8, characterized in that the aforementioned reference is preferably formed from a plurality of consecutive reference values or can be described as a continuous reference curve in relation to time.

10. Arrangement according to claim 8 or 9, characterized in that the motion control (4) comprises means for deriving some references (8, 9, 10, 1 1 , 14, 15, 16, 17) of motion of the transport appliance directly or indirectly from the aforementioned first reference of motion of the transport appliance.

11 .Arrangement according to any of claims 8 - 10, characterized in that the arrangement comprises a measurement (6) of motion, and the motion control (4) is fitted to compare one or more measured values (6) of motion of the transport appliance to the maximum permitted limit value (14) of motion of the transport appliance and possibly also to the minimum permitted limit value (15) of motion of the transport appliance and in that when the measured value deviates outside the range defined by the permitted limit values the transport appliance is fitted to activate an emergency stop.

12. Arrangement according to any of claims 8 - 11 , characterized in that the arrangement comprises a determination of the mechanical vibration of the transport appliance (18, 19, 20) and in that the motion control (4) is fitted to select the frequency and possibly also the harmonic of the frequency of the aforementioned sine function to deviate from the determined mechanical vibration frequency of the transport appliance.

13.An arrangement or method according to any of the preceding claims, characterized in that the aforementioned transport system (7) is an elevator system.