JPH08203161A - Tape tension controller - Google Patents

Abstract

PURPOSE: To keep tape tension constant even if rotational speed of a supply motor is increased. CONSTITUTION: A supply reel winding radius calculating means 41 calculates a winding radius rs' from pulses Pωs and Pωt having frequencies being proportional to rotational speed of a supply reel and a take-up reel. A multiplier 49 multiplies the winding radius rs' by target tension Td and outputs torque M', a driving current calculating means 51 divides torque M' by a supply motor torque constant Kt and calculate a current i', a driving voltage calculating means 53 multiplies the current i' by supply motor armature resistance R and calculates driving voltage E''. A supply reel rotational speed calculating means 57 calculates reel rotational speed ωs' from the pulse Pωs, a rotational speed calculating means 63 divides the rotational speed ωs' by a deceleration ratio Z and calculates supply motor rotational speed ωs'', a counter electromotive force calculating means 65 multiplies the rotational speed ωs'' by a counter electromotive force constant Ke and calculates a counter electromotive force Ve'. A subtracter 55 supplies voltage E' in which the counter electromotive force Ve' is subtracted from the driving voltage E'', to a supply motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tape tension controller for a magnetic tape recorder such as a VTR.

[0002]

2. Description of the Related Art For example, a magnetic tape recording device such as a VTR is provided with a tape tension control device to stabilize tape running. To control the tape tension, there is a closed loop control method in which the tension information obtained from the tape tension detecting element is fed back to the reel motor which is the tension generating means. However, this control method is not effective because of a vibration problem of the tension detecting element itself when the tape is running at a high speed.

Therefore, an open loop control system which does not use the output of the tension detecting element has been widely used during high speed tape running.

FIG. 3 shows the overall structure of a conventional magnetic tape recording apparatus adopting an open loop control system.

The tape 101 emerges from the supply reel 103, passes the path formed by the guides 105, 107 and 109, and reaches the drum 109. The tape 101 exiting the drum 109 passes through the guides 113, 115, 117 and further between the capstan 119 and the pinch roller 121, and is taken up by the take-up reel 125. Tape 10
1 is conveyed by being sandwiched between a capstan 119 and a pinch roller 121. The means for generating the tape tension T is the supply reel motor 127 that generates the brake torque M on the supply reel 103.

The open loop control system is as follows. First, from the supply rotation speed detection element 131 and the winding rotation speed detection element 133 attached to the supply reel 103 and the take-up reel 125, respectively, pulses Pωs and Pωt having frequencies proportional to the rotation speeds of the supply reel and the take-up reel are obtained.
Are supplied to the tape tension control device 140. The supply reel winding radius calculation means 150 uses the pulses Pωs and P
The supply reel winding radius rs' is calculated from ωt. This r
s ′ and the target tension Td are the drive voltage calculation means 160.
And the drive voltage calculation means 160 calculates the drive voltage E ′. The motor driver 170 power-amplifies the drive voltage E ′ to obtain the drive voltage E, and the supply motor 127
Supply to. The supply motor 127 generates the brake torque M by the drive voltage E.

FIG. 4 shows a conventional tape tension control device 140. The supply reel winding radius calculation means 150 includes a supply reel 103 and a take-up reel 125 from a supply rotation speed detecting element 131 and a winding rotation speed detecting element 133 (not shown).
The supply reel winding radius rs' is calculated from the pulses Pωs and Pωt having a frequency proportional to the rotation speed of the.

The multiplier 161 has a supply reel winding radius rs'.
Is multiplied by the target tension Td to output the brake torque M '. The drive current calculation means 163 divides the brake torque M ′ from the multiplier 161 by the torque constant Kt of the supply motor 127 to calculate the drive current i ′. The drive voltage calculation means 165 multiplies the drive current i ′ from the drive current calculation means 163 by the armature resistance R of the supply motor 127,
The drive voltage E'is calculated and output.

[0009]

When the radius of the supply reel is small and the rotation of the supply motor is fast, the counter electromotive force inside the supply motor cannot be ignored, and as a result, the tape tension increases as compared with the target value. However, the conventional tape tension control device has a drawback that it cannot prevent it.

Therefore, it is an object of the present invention to provide a tape tension control device which keeps the tape tension constant regardless of the change in the rotation speed of the supply motor.

[0011]

In a tape tension controller for controlling a brake torque of a supply motor connected to a supply reel to keep a tape tension constant, a first rotation speed for detecting rotation speed information of the supply reel. Detecting means, second rotating speed detecting means for detecting rotating speed information of the take-up reel, and supply reel winding radius calculating means for calculating a supply reel winding radius from outputs of the first and second rotating speed detecting means. And drive motor rotation speed calculation means for calculating the rotation speed of the drive motor of the supply reel from the output from the first rotation speed detection means, and the drive of the supply reel from the output of the drive motor rotation speed calculation means. Back electromotive force calculating means for calculating the back electromotive force of the motor, target tension and the supply reel winding radius from the supply reel winding radius calculating means Comprises a driving voltage calculation means for calculating the driving voltage of the driving motor of the supply reel from said counter electromotive force from the counter electromotive force calculating means.

[0012]

The supply reel winding radius calculating means calculates the supply reel winding radius from the rotation speed information of the supply reel and the take-up reel from the first and second rotation speed detecting means.

The drive motor rotation speed calculation means is the first
The rotation speed of the supply reel drive motor is calculated from the rotation speed information of the supply reel from the rotation speed detection means. The back electromotive force calculation means calculates back electromotive force from the rotation speed of the drive motor from the drive motor rotation speed calculation means.

The drive voltage calculating means calculates a drive voltage from the supply reel winding radius and the target tension from the supply reel winding radius calculating means, and calculates the back electromotive force calculated by the back electromotive force calculating means from the drive voltage. Subtract and output. The output of the drive voltage calculation means becomes the drive voltage of the drive motor of the supply reel.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an outline of a magnetic tape recording apparatus adopting the tape tension control apparatus of the present invention.

Reference numeral 11 is a model of the controlled object. The armature resistance R of the supply motor, the torque constant Kt of the supply motor, the winding radius rs of the supply reel, the winding radius rt of the winding reel, and the reverse of the supply motor. It can be approximated by the electromotive force constant Ke. However, the unit system is the SI unit system.

The adder 13 adds the drive voltage E from the motor driver 37 and the back electromotive force Ve. This adder 13
Output contributes to the generation of the brake torque of the supply motor (not shown). The circuit 15 divides the output of the adder 13 by R to obtain the current i. The circuit 17 generates the brake torque M by multiplying the current i by Kt. The circuit 19 divides the brake torque M by rs to obtain the tape tension T.

On the other hand, the tape speed V is determined by the speed of a capstan (not shown) or a take-up reel (not shown). In circuit 21, divide tape speed V by rs,
Then, multiplying by 2π gives the supply reel rotation speed ωs. Similarly, in the circuit 23, when the tape speed V is divided by rt and multiplied by 2π, the take-up reel rotation speed ωt
Becomes

The circuit 25 sets the supply reel rotation speed ωs to K.
e is multiplied and the above-mentioned counter electromotive force Ve is output.

The supply reel rotation speed ωs is detected by the supply rotation speed detection element 31, and the take-up reel rotation speed ωt is detected by the winding rotation speed detection element 33. The respective outputs are pulses Pωs and Pωt having a frequency proportional to the rotation speed. Is. The pulses Pωs and Pωt are supplied to the tape tension controller 35. The output of the tape tension controller 35 has a drive voltage of E '. The motor driver 37 is
The drive voltage E ′ is power-amplified and the drive voltage E is controlled 1
Feed to 1.

The above-mentioned R, Kt, Ke, and the reduction ratio Z described later are measured in advance.

FIG. 2 is a block diagram showing the configuration of the tape tension control device 35 of the present invention. The pulses Pωs and Pωt are input to the circuits 43 and 45 of the supply reel winding radius calculation means 41, respectively. The circuit 43 outputs the pulse Pωs
Is calculated and is multiplied by N (the number of pulses for one round of the reel) to calculate Tωs (Tωs is the rotation cycle of the supply reel). The circuit 45 obtains the reciprocal of the pulse Pωt and multiplies this by N to obtain Tωt (Tωt is the rotation cycle of the supply reel). The circuit 47 is a constant (Ka) obtained from the ratio of Tωt and Tωs and the total tape length.
((Reel hub radius ^{) 2} + (maximum winding radius ^{) 2} ) is used to execute the calculation of the following equation (1), and the supply reel winding radius r
Calculate s'.

[0023]

[Equation 1] The multiplier 49 multiplies the supply reel winding radius rs 'by the target tension Td and outputs the brake torque M'. The drive current calculation means 51 divides the brake torque M ′ from the multiplier 49 by the torque constant Kt of the supply motor (not shown) to calculate the drive current i ′. Drive voltage calculation means 53
Calculates the drive voltage E ″ by multiplying the drive current i ′ from the drive current calculation means 51 by the armature resistance R of the supply motor.

Circuit 43 of supply reel winding radius calculation means 41
Is supplied to the supply reel rotation speed calculation means 57. It should be noted that another circuit 43 may be added to the supply reel rotation speed calculation means 57. The circuit 59 has an input T
The reciprocal of ωs is calculated and Pωs ′ is output. Circuit 61
Outputs the supply reel rotation speed ωs 'by multiplying the output Pωs' of the circuit 59 by 2π.

The rotation speed calculation means 63 divides the supply reel rotation speed ωs' from the circuit 61 by the reduction ratio Z (for example, 1 in the direct drive system) to calculate the rotation speed ωs "of the supply motor. The counter electromotive force calculation means 65 is
Rotational speed ω of the supply motor from the rotational speed calculation means 63
The counter electromotive force Ve 'is calculated by multiplying s "by the counter electromotive force constant Ke of the supply motor.

The subtractor 55 subtracts the back electromotive force Ve ′ calculated by the back electromotive force calculation means 65 from the drive voltage E ″ calculated by the drive voltage calculation means 53, and supplies the output E ′ to the motor drive 37. .

As described above, the tape tension control device 35 is
Since the back electromotive force Ve ′ calculated by the back electromotive force calculation unit 65 is subtracted from the drive voltage E ″ calculated by the drive voltage calculation unit 53 and supplied to the supply motor, even if the rotation speed of the supply motor increases, the tape The tension can be kept constant.

[0028]

According to the present invention, it is possible to realize a tape tension control device which has a simple structure and makes the tape tension constant regardless of the change in the rotation speed of the supply motor.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a magnetic tape recording device adopting a tape tension control device of the present invention.

FIG. 2 is a block diagram showing a configuration of a tape tension control device of the present invention.

FIG. 3 is a diagram showing an overall configuration of a magnetic tape recording device that employs a conventional tape tension control device.

FIG. 4 is a block diagram showing a configuration of a conventional tape tension control device.

[Explanation of symbols]

11 ... Modeling of controlled object, 31 ... Supply rotational speed detecting element, 33 ... Winding rotational speed detecting element, 35 ... Tape tension control device, 37 ... Motor driver, 41 ... Supply reel winding radius calculating means, 49 ... Multiplier , 51 ... Drive current calculation means, 53 ... Drive voltage calculation means, 55 ... Subtractor, 57 ...
Supply reel rotation speed calculation means, 63 ... Rotation speed calculation means, 65 ... Back electromotive force calculation means.

Claims (3)

[Claims] 1. A tape tension control device for controlling a brake torque of a supply motor coupled to a supply reel to keep a tape tension constant, and a first rotation speed detecting means for detecting rotation speed information of the supply reel, Second rotation speed detecting means for detecting rotation speed information of the take-up reel; supply reel winding radius calculating means for calculating a supply reel winding radius from outputs of the first and second rotation speed detecting means; Drive motor rotation speed calculation means for calculating the rotation speed of the drive motor of the supply reel from the output from the rotation speed detection means of No. 1, and back electromotive force of the drive motor of the supply reel from the output of the drive motor rotation speed calculation means. Counter electromotive force calculating means for calculating electric power; target tension, supply reel winding radius from the supply reel winding radius calculating means, and counter electromotive force calculation And a drive voltage calculation unit that calculates a drive voltage of the drive motor of the supply reel from the counter electromotive force from the output unit. 2. The drive motor rotation speed calculation means calculates the rotation speed of the supply reel from the output of the first rotation speed detection means, and the output of the supply reel rotation speed calculation means. And a rotation speed calculation means for dividing the ratio by a reduction ratio.
The tape tension control device described. 3. The drive voltage calculation means calculates a torque by multiplying an output of the supply reel winding radius calculation means by a target tension, and a driving means for driving the supply reel with the torque from the multiplication means. Driving current calculation means for calculating the driving current by dividing by the torque constant of the motor, and the driving current from the driving current calculation means is multiplied by the armature resistance of the driving motor of the supply reel to obtain the driving voltage. 3. A driving voltage calculation means for calculating, and a subtraction means for subtracting the back electromotive force from the back electromotive force calculation means from the drive voltage from the drive voltage calculation means. The tape tension control device described.