DE3105173A1 - Controllable positioning system for recording and reproducing apparatuses, in particular for video apparatuses with longitudinal track recording - Google Patents

Abstract

A controllable positioning system for recording and reproducing apparatuses, in particular for video apparatuses with longitudinal track recording, is described. In the case of such apparatuses, the difficulty and complexity involved in video head switching and tracking control with extreme precision and greatest possible speed present a great problem. To solve this problem, according to the invention as shown in Fig. 1, a control system responsible for accuracy and a pulse generating stage for accelerating and braking pulse trains, responsible for the high switching speed, are provided, in which arrangement a switching device is used in the "normal mode" to close the control loop to form an output stage connected to a balancing stage and having a transformer connected to it, and to switch over to the pulse generating stage at the beginning of a movement cycle of the video head and not switch back to the control loop until the accelerating and braking operation for a head movement stage has been completed. <IMAGE>

Description

ADJUSTABLE POSITIONING SYSTEM FOR RECORDING AND PLAYBACK DEVICES, IN PARTICULAR FOR VIDEO EQUIPMENT WITH LONGITUDINAL TRACK RECORDING DESCRIPTION The invention refers to an adjustable positioning system for recording and playback devices, especially for video devices with longitudinal track recording, according to the generic term des. Claim 1., In various longitudinal track video recording systems (LVR systems) the transition must be made at the end of a video track within a very short time (e.g. 20 ms) to the next track. This means a displacement of the record / playback head by a certain amount (level). To exchange magnetic tapes or video cassettes to enable interference-free with other devices of the same system (compatibility), you need a track adjustment option at the same time; also allowed between Self-recording and self-playback no tracking errors occur, i.e. neither from step to stage still from the first stage to the last stage. The control range should be as close as possible be large in order to catch them quickly and safely, even with large deviations To ensure that it engages on the target track. When the video head has taken its position it must also be mechanically stable, i.e. vibrations must not change position of the video head.

From DE-OS 28 49 110 an electronic blocking device is known for DC motors, in which the closest with the help of a position detector Position point of a rotating part is detected and a negative feedback to the direction of rotation begins, whereby the edge of the positive feedback is automatically skipped.

The invention is based on the object of a controllable positioning system for recording and reproducing devices, in particular video devices with longitudinal track recording to create, with which a video track or video head switching and track adjustment with the highest precision and high speed is made possible, with expensive mechanical Components can be omitted and the accuracy cheap and without great effort the production (post-processing, etc.) is to be achieved.

This object is achieved according to the invention by the features in the characterizing part of the claim 1 specified features solved.

Advantageous embodiments of the positioning system according to the invention result from the subclaims.

With the positioning system according to the invention, the greatest possible Speed when changing the position of the video head with maximum precision Achieved from level to level, since no addition and repetition errors occur. Due to the simple and cheap construction - cheap electronics replace expensive mechanics, such as B. stepper motors - can the step accuracy without great effort, d. H. for example, without labor-intensive mechanical processing or post-processing in and for the production of accuracy.

In addition, the video head retains its position mechanically stable by the control system, so that z. B. Vibrations no change in position of the video head. The positioning system according to the invention also fulfills the above-mentioned requirements for lane readjustment options and related Compatibility with the tape or Exchange of cassettes with other video devices (same Systems), with the video head being tracked electronically. It also shows that in the event of large track deviations, the video head quickly moves to or into the correct position (Track position) is regulated.

The invention is described below with reference to the drawing figures, for example explained in more detail.

1 shows the basic structure of an inventive Positioning system in the form of a block diagram, Figure 2 is a block diagram an acceleration / braking pulse generation as provided in accordance with FIG. 1 and FIG. 3 pulse diagrams for different switching states of the circuit according to FIG. 1 or 2.

The mode of operation of the positioning system according to the invention is below in connection with the description of the block diagrams according to Fig. 1 (basic structure) and Fig. 2 (acceleration and braking pulse generation) explained: The circuit generally consists of a control system 1, 2, 3 with a Control amplifier 1, a position indicator 2 and a reference 3, a switching device 4 and a pulse generator level 5 for acceleration / braking pulses (adjustable Acceleration time and braking time).

The control system 1, 2, 3 is responsible for the accuracy; a pulse train of acceleration and braking for the high speed of level switching.

An output stage 6 with adjustable overall gain is for the moment accelerating and braking fully switched through in the respective direction, so that a maximum current can flow. When this process is finished, the controlled by a specified phase setpoint by reference 3.

According to the structure according to FIG. 1, the actual value input of the control amplifier is 1 is connected to the output of the position detector 2, the input side to the output an electromechanical converter 7 is connected. The output voltage of the reference stage 3, which receives the signal for the tracking on the input side and thereby influences it is fed to the setpoint input of control amplifier 1, its output with one contact terminal E 1 of the switching device 4 is connected. Output side the switching device 4 is connected to one input of the output stage 6, while the other input receives the output signal of a balancing stage8. The output signal the output stage 6 is fed to the input of the converter 7. The switching contact of the Switching device 4 is (via its input S) from the output signal of the pulse generator stage 5 actuated, with a further output of the pulse generator stage 5 with the others Kontaktarschluss E 2 of the switching device 4 is connected. At the two entrances of the pulse generator stage 5 (acceleration and braking pulse time) are for the direction-dependent Acceleration and braking pulse generation the keys T1 and T2 connected.

The position indicator 2 must allow a direct voltage transmission. Accordingly, z. B. an optocoupler with a light source, a segment disk and a phototransistor or a Hall generator with magnet segments can be used. The slot width of the receiver in an optocoupler essentially depends the readjustment range of the video head. The slot width is determined according to the scanning law the steepness of the flanks (camera tubes flying spot scanner). You should if possible be large, but must not exceed the size of a segment. You then get a control range of approx.

+ 1/2 step.

The control amplifier 1 is usually a PID controller with controllable P component. Since the residual error of the control is already negligible with a PD controller is small, an integral component can be dispensed with. The differentiating Behavior (D component) is essential for the control to engage particularly quickly.

By using a PD controller (for motors with inertia) the proportional part can be significant be enlarged (decrease of the residual error). In addition, the limitation required for a pure P controller is not applicable the motor current (tendency to oscillate due to inertia), d. H. you also get larger ones Control deviations result in a proportionally increasing torque and thus a faster one Capture than with pure P-controller circuits.

The output stage 6 with the balancing stage 8 connected to it has two functions. As. first it must for a sufficient current gain between Acceleration-braking pulse and electromechanical converter 7 provide.

Second, it must have electrical and mechanical tolerances between the forward and backward movement of the video head. this happens by shifting the medium voltage of the output stage 6 until the correct one Acceleration / braking current ratio of a forward and reverse stage set is and the electromechanical converter 7 after a forward and backward stage'auch returns to the old position without regulation.

In the simplest case, the electromechanical converter 7 consists of one DC motor with a tightly coupled helical coil, the adjustment errors the segment disk of the optocoupler divided down by the factor of the reduction. To get away from the adjustment errors. A linear motor can also freeze up link can be used for the video head and the segment strip.

In this case, the helix would also be omitted.

The normal reference voltage (setpoint outputs at the reference stage 3) corresponds to the average edge value of position detector 2. One that deviates from this Reference voltage inevitably leads to a change in position until the edge value corresponds to the set reference.

The pulse control circuit changeover switch (changeover device 4) in FIG. 1 is switched in normal operation so that the control loop is closed. The electromechanical Converter 7 is now held at a setpoint value predetermined by reference 3. At the beginning of a motion cycle of the video head, the switching device 4 switched to pulse generation and only then switched back to the control loop, when the acceleration and deceleration for one head movement stage is completed is.

In the block diagram of the acceleration / braking pulse generation according to Fig. 2, which illustrates the pulse generator stage 5 of Fig. 1: in more detail the two buttons T 1 and T 2 with the bath inputs of a direction identification stage 51 connected, the output side with a clock generator stage 52 (e.g. multivibrator) and a direction switch 56 is connected, wherein at the signed The position of the input R corresponds to "low". The output side (clock line Cl) .is the Clock generator stage 52 to the input of a first monostable multivibrator (mono-flop) 53 connected for acceleration (adjustable acceleration time). The exit Q1 of the first mono-flop 53 is fed to one input of an OR gate 55, while the negated output Q1 with a second monostable trigger circuit mono-flop) 54 for braking (adjustable braking time) is connected. , The output Q2 of the mono-flop 54 leads to the other input of the OR gate 55 and to the one contact connection of the direction switch 56, while the other contact connection with the negated Output Q2 of the mono-flop 54 is connected. The outputs of the OR gate 55 and of the direction switch 56 lead to the inputs S resp.

E 2 of the switching device 4 from FIG. 1.

The time for the switching process is specified in the system. She shares roughly three parts for the acceleration and two parts for the braking process on. The fine adjustment is made dynamically, to the shortest and smallest overshoot the control voltage. Only then is the transient process of the control voltage fast completed. For a forward or backward movement of the video head, only one is negated Acceleration / braking pulse necessary.

The function shown in Fig. 3 ~ or. Pulse diagrams apply on the one hand for the behavior of the positioning system according to the invention when pressed Button T 1 (Fig. 3a) or if button T 2 is pressed (Fig.

3b) '. The individual pulse trains represent the output voltages at the outputs of the individual circuit parts labeled with the same reference numerals 1 and 2 respectively. Accordingly, the pulse sequence Q1 thus means the output voltage at the non-inverted output Q1 of the mono-flop 53, while C1 represents the clock, etc. In the representation for the motor current are "Control", "Accelerate", "Braking" and "transient process" recognizable.

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Claims (6)

ADJUSTABLE POSITIONING SYSTEM FOR RECORDING AND PLAYBACK DEVICES, IN PARTICULAR FOR VIDEO DEVICES WITH LONGITUDINAL TRACK RECORDING 'PATENT CLAIMS @ Adjustable.positioning system for recording and playback devices, in particular for video devices with longitudinal track recording, with a control loop with control amplifier, reference stage and position indicator as well an output stage connected to the control amplifier, which is connected to the position indicator connected electromechanical transducer is connected, g e k e n n z e i c-h n e t d u r c h - one between the output of the control amplifier (1) and the input the switching device (4) connected to the output stage (6) - a pulse generator stage (5) for acceleration and braking pulses, which are sent to one of the outputs on the output side Contact connection (E 2) and the switching contact (5 ') connected to the output stage (6). connected and - a balancing stage (8) connected to the output stage (6). 2. Controllable positioning system according to claim 1, d a d u r c h g e k e n n n z e i c h -n e t that the pulse generator stage (5) is a direction identification stage (51), an associated clock generator stage (52) to which a first monostable Trigger circuit (53) is connected and a second monostable trigger circuit (54), an OR gate (55) and a direction switch (56), the non-negated outputs (QliQ2) of the trigger circuits (53; 54) to the two inputs of the OR gate (55) and its. Output to the switching contact (S) of the switching device (4) are connected while the negated output (Q1) of the first flip-flop (53) is connected to the second flip-flop (54) whose negated output (Q2) to one contact connection and its non-negated output (Q2) to the other contact connection of the direction switch (56) is performed, which is also on the input side with the direction identification stage (51) and on the output side with one contact connection (E. 2j of the switching device (4) is connected. 3. Controllable positioning system according to claim 1 or 2, d a d u r c h e k e n n n z e i c h n e t that, the position indicator (2) after the optocoupler or Hall generator principle works. 4. Controllable positioning system according to claim 1 or 3, d a d u r c h e k e n n z e i e-h n e that for. the control amplifier (1) a PID or PD controller is provided. 5. Controllable positioning system according to one of claims 1 to 4, that is for the electromechanical Converter (7) a direct current motor with a tightly coupled helix or a linear motor with a rigid connection to the video head and the segment strip of the optocoupler is. 6. Controllable positioning system according to one of claims 1 to 5, that the switching device (4) closes the control loop in "normal operation", while at the beginning of a video head movement cycle the switching device (4) switches to the pulse generator stage (5) and then switches back to the control loop when the acceleration and braking process for one. Video head movement stage is finished. Description: