EP1310941B1

EP1310941B1 - A method and a device for controlling a pendulum angle of a bell

Info

Publication number: EP1310941B1
Application number: EP01204313A
Authority: EP
Inventors: Gerrit c/o Clock-O-Matic N.V. Van Elst
Original assignee: Clock-O-Matic Nv
Current assignee: Clock-O-Matic Nv
Priority date: 2001-11-09
Filing date: 2001-11-09
Publication date: 2010-06-02
Anticipated expiration: 2021-11-09
Also published as: EP1310941A1; ATE470215T1; DE60142298D1

Abstract

A method for controlling a pendulum angle of a bell, in particular a church bell, wherein a pendulum movement of said bell is powered by a pulsewise driven electrical motor, in particular an asynchronous motor, wherein during a first phase of a repetitive control cycle a powerpulse is supplied to said motor, and wherein, during a second phase of said control cycle where no power is supplied to said motor and which follows said first phase, a DC voltage is appied on said motor in order to generate a time signal indicating an actual time period for said pendulum movement, said time signal being compared with a predetermined time period for said pendulum movement in order to determine a correction value if said actual period is different from said predetermined time period. <IMAGE>

Description

The invention relates to a method for controlling a pendulum angle of a bell, in particular a church bell, wherein a pendulum movement of said bell is powered by a pulsewise driven electrical motor, in particular an asynchronous motor, wherein during a first phase of a repetitive control cycle a powerpulse is supplied to said motor, and wherein, during a second phase of said control cycle where no power is supplied to said motor and which follows said first phase, a DC voltage is applied on said motor in order to generate a time signal indicating an actual time period for said pendulum movement, said time signal being compared with a predetermined time period for said pendulum movement in order to determine a correction value if said actual period is different from said predetermined time period, and wherein said powerpulse is adjusted under control of said correction value.
Such a method is known from EP-A-1094443 . The control cycle of the motor driving the bell comprises two phases, namely a first one wherein power is supplied to the motor in order to drive the bell and a second one where no power is supplied. During the second phase a DC voltage is applied to one coil of the three phase asynchronous motor. This causes that, in the powerfree condition wherein the motor is during this second phase, two AC voltages are generated in the other coils of the motor, which voltages are phase shifted with respect to each other. These voltages are generated due to the fact that the motor is driven in that second phase by the movement of the clock itself. Since those voltages become zero at the reverse point within the pendulum movement, it becomes possible to deduce therefrom an average time signal indicating an actual time of the pendulum movement. As the time deviation is not always the same, due to the oscillation phase, several pendulum movements have to be measured to determine the correct time period. This time period (Ist-value) can then be compared with a predetermined time period (Soll-value) indicating the correct time period of the pendulum movement, in order to verify if the motor correctly drives the bell. If the compared time periods do not correspond with each other, then a correction value can be determined based on the difference between the time periods. The powerpulse supplied to the motor can then be adjusted under control of the determined correction value. In such a manner the bell can be suitable driven in order to produce a correct bell sound.
A drawback of the known method is that this method is only applicable to a three phase motor. Indeed, the DC voltage is applied to one coil and generates a voltage in the other coils due to the movement of the bell. So the known method is not applicable to a single phase motor. Further it is necessary to take into account several time periods in order to obtain a reliable time signal.
It is an object of the invention to provide a method for controlling a pendulum angle of a bell, which method is also applicable to a single phase motor.
For this purpose a method according to the invention is characterised in that said second phase corresponds to a direction reverse within said pendulum movement, and wherein said DC voltage is applied to said motor in order to generate an EMF within said motor, which EMF is monitored in order to determine each time within said second phase a time moment at which said EMF reaches a peak value, said time signal being determined by determining each time a time duration between said time moments of successive second phases. The EMF (Electromotive Force) is generated in the coil where the DC current is applied in a period wherein the pendulum movement reverses. This movement reverse will create a peak value in the generated EMF during each pendulum time period. So, by measuring the time duration between successive peaks, the time period of the pendulum movement is determined. Since the EMF is generated in the coil wherein the DC voltage is applied, the method according to the invention is applicable to a single phase motor. Since the time signal is determined for each time period of the pendulum movement, the exact time duration can be measured, so that a fast control of the pendulum movement can be assured and a minimum deviation can be controlled.
A first preferred embodiment of a method according to the invention is characterised in that said EMF is monitored by measuring a current induced in said motor and by establishing when said current reaches a maximum value. A current measurement is a reliable method for determining the peak value.
Preferably said time moment is each time stored into a memory, said time duration being determined by deducing said stored time moment from an actual determined time moment. This renders the calculation of the time duration easy.
The invention also relates to a device for controlling a pendulum angle of a bell.
The invention will now be described in more details with reference to the drawings illustrating a preferred embodiment of the invention. In the drawings :

fig. 1 illustrates schematically a device according to the invention and connected to a bell;
fig. 2 illustrates control signals generated by the control member; and
fig. 3 illustrates by means of a diagram the method according to the invention.

The device illustrated in figure 1 comprises a control circuit 14 connected to supply lines 5 feeding an electrical motor 4 with electrical power. The motor is preferably an asynchronous AC induction motor since it has to reverse its rotational movement frequently. The motor 4 drives a bell 1 fixed on a drive wheel 2 which is connected to the motor for example by means of a belt or a chain 3. The motor drives the drive wheel 2 in two opposite rotational directions in order to impose a pendulum movement with a pendulum angle α on the bell. The value of the pendulum angle α is predetermined in order to obtain a correctly defined pendulum movement leading to a clear and harmonious bell sound. During each pendulum period of the bell the motor is powered in order to maintain the bell at the correct pendulum angle.
The powering of the motor is controlled by a control member 7, for example formed by a microprocessor and an A/D converter. The control member is connected to a control input of a first switch 6 mounted in the AC power supply line 5 and to a control input of second switch 13 which power output is connected via line 8 to the one or two of the supply lines 5, depending whether the motor is single or plural phase. A DC supply source 10, for example formed by a capacitor or a battery, is connected between a power input of the second switch and via a shunt resistor 11 to another supply line 5, different from the one to which the power output of the second switch is connected. The inputs of an isolation amplifier 12 are connected over the shunt resistor 11 and an output of the amplifier 12 is connected to a signal input of the control member 7.
The pendulum movement of the bell is powered by the pulsewise driven electrical motor 4. During a first phase F1, as illustrated in figure 2, of a repetitive control cycle governed by the control member 7, the latter generates a first control signal CS 1 which is supplied to the first switch 6, causing the latter to close. In such a manner a powerpulse is supplied to the motor 4 causing the latter to drive the bell 1. During a second phase F2, following the first phase, the first control signal goes down, causing the first switch 6 to open and thus to interrupt the power supply to the motor. During that second phase the pendulum movement of the bell will not be powered and the bell will run free. The first and second phase are adjusted in such a manner with respect to the bell movement that the second phase corresponds each time with the period during which the pendulum movement has reached its maximum amplitude and reverses.
During that second phase, the control member also generates a second control pulse CS 2, as illustrated in figure 2. That second control pulse is applied to the second switch 13 causing the latter to close. The DC voltage of for example 8 V, supplied by the DC supply source 10 is thus supplied to the motor during that second phase. The DC voltage is applied to one or two coils of the motor, depending whether the latter is a single phase or not. This explains why the second switches 13 are connected in parallel with respect to the DC supply source 10. By applying this DC voltage to the motor an EMF (Electromotive Force) is generated with the motor. This EMF generates a DC current of for example 100mA, depending on the motor power which will flow in the motor coils, causing a slight speed reduction of the bell movement which runs free since the motor is not powered during the second phase. The EMF or DC current induced in the motor during that second phase is monitored by the control member 7 using therefor the signal supplied at its signal input by amplifier 12. The monitored DC current is illustrated in figure 3.
Since the second phase corresponds with the period where the pendulum movement has reached its maximum amplitude and reverses, this reverse in the pendulum movement is transmitted to the motor by means of the transmission belt 3. Due to this reverse the current induced in the motor by the applied DC voltage will rise to a maximum or peak value during that second phase, as illustrated in figure 3.
The time moment (T1, T2) at which the peak value is reached, is each time determined. At the end of the second phase the second signal goes down thereby opening the switch 13. This causes the DC-voltage to be no longer applied to the motor and the EMF no longer generated as illustrated in figure 3. The second phase is followed by a new first phase and the control cycle is repeated. Since during each second phase an EMF is generated in the motor, during each second phase a peak value will be observed in the EMF. The time moment T1, T2, is each time determined which enables to determine a time duration Δt = T2-T1 during two successive peak values. Since the peaks occur at a reverse moment of the pendulum movement, the time duration Δt corresponds to a complete pendulum movement of the bell. So by monitoring the peak's value, the pendulum time period can be determined for each complete pendulum movement. Since the latter is directly proportional to the pendulum angle, the pendulum angle can also be determined.
In order to determine Δt, the values of T1 and T2 are each time stored in a memory of the control member 7. Once T2 is determined, the value of T1 is read from the memory and Δt is determined by deduction T2 - T1. The read value is each time overwritten by the newly determined value in order to efficiently use the memory space available.
The value of Δt enables now to determine a time signal indicating the actual time period of the pendulum movement. In order to check if Δt (Ist-value) corresponds with a correct pendulum angle and thus with a predetermined time period ΔT (Soll-value) for the pendulum movement, the value of Δt is compared with ΔT, for example by a deduction ΔT - Δt, in order to determine a correction value. If ΔT - Δt = 0 or is within a predetermined range, the correction value is zero and no adjustment of the powerpulse is realised. If on the other hand the control member established that |ΔT-Δt| > 0 or higher than a predetermined value, then the correction value is different from zero and the value of the powerpulse is adjusted in order to have the bell balancing according to the correct pendulum angle. The adjustment of the powerpulse is for example realised by means of a PI regulator which is controlled by the value ΔT - Δt.

Claims

A method for controlling a pendulum angle of a bell, in particular a church bell, wherein a pendulum movement of said bell is powered by a pulsewise driven electrical motor, in particular an asynchronous motor, wherein during a first phase of a repetitive control cycle a powerpulse is supplied to said motor, and wherein, during a second phase of said control cycle where no power is supplied to said motor and which follows said first phase, a DC voltage is applied on said motor in order to generate a time signal indicating an actual time period for said pendulum movement, said time signal being compared with a predetermined time period for said pendulum movement in order to determine a correction value if said actual period is different from said predetermined time period, and wherein said powerpulse is adjusted under control of said correction value, characterised in that said second phase corresponds to a direction reverse within said pendulum movement, and wherein said DC voltage is applied to said motor in order to generate an EMF within said motor, which EMF is monitored in order to determine each time within said second phase a time moment at which said EMF reaches a peak value, said time signal being determined by determining each time a time duration between said time moments of successive second phases.
A method as claimed in claim 1, characterised in that said EMF is monitored by measuring a current induced in said motor and by establishing when said current reaches a maximum value.
A method as claimed in claim 1 or 2, characterised in that said time moment is each time stored into a memory, said time duration being determined by deducing said stored time moment from an actual determined time moment.
A method as claimed in anyone of the claims 1 to 3, characterised in that said time duration is each time converted into a pendulum angle value.
A method as claimed in anyone of the claims 1 to 4, characterised in that said DC voltage is applied on a single phase motor.
A method as claimed in anyone of the claims 1 to 4, characterised in that said DC voltage is applied on a plural phase motor.
A device for controlling a pendulum angle of a bell, in particular a church bell, said device comprising a control member having an input and an output provided to be connected to an electrical motor, in particular an asynchronous motor, provided to pulsewise drive a pendulum movement of said bell, said control member being provided to enable during a first phase of a repetitive control cycle a supply of a powerpulse to said motor and during a second phase of said control cycle, where no power is supplied to said motor and which follows said first phase, to apply a DC voltage on said motor in order to generate a time signal indicating an actual time period for said pendulum movement, said control member further comprising a comparator provided to compare said time signal with a predetermined time period for said pendulum movement in order to determine a correction value if said actual period is different from said predetermined time period, and wherein said control member further comprises means for adjusting said powerpulse under control of said correction value, characterised in that said second phase corresponds to a direction reverse within said pendulum movement, and wherein said DC voltage is applied to said motor in order to generate an EMF within said motor, said control member comprises means for monitoring said EMF in order to determine each time within said second phase a time moment at which said EMF reaches a peak value, said time signal being determined by determining each time a time duration between said time moments of successive second phases.