[0019] Refer to Figure 3, which is a schematic diagram of a stepping motor to illustrate the control method of the stepping motor 300. The stepping motor is used as the trolley motor as described above, which includes a rotor 310 and a phase A stator. 302, a phase B stator 304, a phase A'stator 306, and a phase B'stator 308, wherein the rotor 310 has a specific magnetic field, so the protruding end of the rotor in the figure will point to a rotor direction in the same direction as the applied magnetic field ; And individual stators can change individual magnetic field directions through external control signals, and synthesize an equivalent magnetic field direction to control the rotor direction. Refer to Figure 4 again, which is a timing diagram for explaining the control signal of the stepping motor to control the excitation frequency of the stepping motor. The control signal of each phase is switched between a high potential and a low potential. It is used to change the direction of the magnetic field of individual stators. By adjusting the control signals of the four phases, the rotation direction and speed of the rotor can be controlled. Note that only a simplified two-phase stepping motor is used in Figures 3 and 4 As an example, those skilled in the art can extend this concept to other types of stepping motors.
[0020] In addition, there are four dashed lines in Figure 3 to indicate four different rotor directions. At the same time, referring to the control signal shown in Figure 4, the period PQRS constitutes a control signal period, and the period P'represents the next The control period corresponds to the above-mentioned P period: an AB direction 322, which is used to indicate that in a period P (or P'), when the phase A stator 302 and the phase B stator 304 are excited by a high potential, the corresponding Rotor direction; a B-A' direction 324, used to indicate the rotor direction corresponding to the phase B stator 304 and the phase A'stator 306 are excited by a high potential in a period Q; a A'-B 'Direction 326' is used to indicate the direction of the rotor when the phase A'stator 306 and the phase B'stator 308 are excited by a high potential in a period of time R; a B'-A direction 328 is used to indicate In a period S, when the phase B'stator 308 and the phase A stator 302 are excited by a high potential, the corresponding rotor direction. When the control signal changes according to the PQRS sequence, the rotor 310 will rotate in a clockwise direction, where the time interval of the PQRS sequence change will correspond to an excitation frequency, and the excitation frequency will correspond to a target speed of the motor; In the state, the rotor 310 of the stepping motor 300 will rotate at the target speed. However, due to various mechanical friction and resistance, the rotor 310 still needs to overcome a static friction torque. If the magnetic field strength is too small, or the The excitation frequency is greater than a critical frequency, wherein the critical frequency corresponds to a target speed Rs, and the critical frequency is the maximum excitation frequency allowed by the stepping motor to overcome the static friction torque, it may happen that the rotor 310 cannot reflect the direction of the stator magnetic field Without any rotation, this phenomenon is generally called out-of-step. This out-of-step phenomenon is known to be avoided when driving a stepping motor.
[0021]To use the stepping motor 300 as the sled motor 142, the maximum moving distance of the sled as described above must first be converted into a total number of sled steps of the stepping motor according to the ratio of the rack 146 and the gear set 144. When the sled homing action is performed, the stepping motor 300 is controlled to rotate the total number of steps of the sled. Consider that when the pulley 234 is homing, if the distance between the initial position of the pulley 234 and the innermost position 242 of the pulley is less than the maximum movement distance of the pulley, the pulley 234 will be restricted to the innermost position 242 of the pulley by the mechanism. , Can no longer move inward; refer to Figures 3 and 4 at the same time, for example, if the rotor direction is the AB direction at this time, the control signals of each phase have the relationship shown in the period P, and the pulley The innermost position 242 does not have the sensing device as in the conventional technology, so when the time reaches the period Q, the rotor 310 should rotate clockwise to the B-A' direction 324 in theory, but because the pulley 234 has been The mechanism is restricted to the innermost position 242 of the trolley, so that the rotor 310 cannot follow the magnetic field to rotate to the B-A′ direction, and the rotor 310 will remain in the AB direction 322. Similarly, when time reaches the period R, the rotor 310 will still remain in the AB direction 322, but when the time reaches the period S, the equivalent magnetic field direction is the B'-A' direction 328. At this time If the target speed of driving the stepping motor 300 is less than or equal to Rs, the rotor 310 will be pulled to the B'-A direction 328, causing the trolley 134 to move a short distance to the outside; In time period P', the rotor 310 is pulled to the AB direction 322 again, so that the trolley 134 moves inward to the innermost position 242 of the trolley; this will produce an oscillating action, causing continuous collision and wear between the mechanism components, and noise , The oscillating action will continue until the end of the control signal relative to the total number of trolley steps.
[0022] In the present invention, in order to further eliminate the oscillating action, and in order not to additionally install the above-mentioned induction device at the innermost position 242 of the trolley, the present invention also proposes a method of driving the stepping motor. The total trolley steps are implemented in two stages, including a motor starting stage and a home driving stage. In the motor starting stage, the stepping motor is driven at a first target speed, the first target speed being less than or equal to The above-mentioned rotation speed Rs. The purpose of the motor starting phase is to overcome the static friction torque. Therefore, when the stepping motor can follow the control signal to rotate, it can enter the home driving phase. At this time, the stepping motor is driven in a home driving mode. The homing drive mode refers to providing a target speed curve to drive the trolley 234 back to the innermost position 242 of the trolley. The target speed curve also includes acceleration or deceleration configurations to obtain the best trolley movement mode, and make the target speed curve. The target speed of the speed curve is greater than the speed Rs. Therefore, when the trolley 234 has reached the innermost position 242 of the trolley, the rotor 310 is stopped in a specific direction, such as the AB direction 322. When the equivalent magnetic field continues to rotate, because the stepping motor is driven at a target rotation speed greater than the rotation speed Rs, the rotor 310 can no longer overcome the static friction torque, or the rotation range of the rotor 310 is extremely small. As a result, the stepping motor 300 is out of step, and therefore the trolley 234 no longer moves to the outside. Therefore, the oscillating action can be eliminated by controlling and using the generally undesirable out of step phenomenon.
[0023] Refer to Figure 5, which is a flow chart for explaining an embodiment of a method for homing control of an optical disc drive according to the present invention, and also refer to Figure 6, which is shown as a coordinate diagram for explaining the method according to the present invention. The control flow in Figure 5 controls the speed of the stepping motor. In step 502, first, in the motor starting phase as described above, the trolley motor is driven at the first target rotation speed. At this time, the target rotation speed of the stepping motor is shown from time 0 to time M; The bit drive mode includes a rotation speed conversion phase and a rotation speed maintenance phase; in the rotation speed conversion phase (step 504), the target rotation speed for driving the stepping motor is gradually converted from the first target rotation speed as described above to greater than the first target rotation speed. A second target speed of the target speed, such as time M to time N in Figure 6, and then in the speed maintenance phase (step 506), after time N in Figure 6, continue to drive the step with the second target speed Into the electric motor. And as mentioned earlier, in the motor starting phase, the rotation speed conversion phase, and the rotation speed maintenance phase, the total number of steps driven by the stepping motor is equal to the total number of trolley steps. Furthermore, because the stepping motor needs to overcome a dynamic friction torque when rotating, the second target rotation speed is less than or equal to a rotation speed Rm, and the rotation speed Rm corresponds to the maximum excitation frequency allowed by the trolley motor to overcome the dynamic friction torque; The second target rotation speed is also greater than a rotation speed Rs, and the rotation speed Rs corresponds to the maximum excitation frequency allowed by the trolley motor to overcome the static friction torque.
[0024] In addition, according to the control method of the present invention, a circuit device (not shown) is responsible for processing the homing action of the trolley. In one embodiment, the circuit device refers to a microprocessor that executes a software. These targets are as described above. The speed and the parameters or calculation rules required for these execution stages are pre-programmed in the software; and in another embodiment, the circuit device refers to a set of logic circuits designed to execute the control method according to the present invention, In addition, the target speeds and the parameters or calculation rules required in these execution stages as described above are directly designed as a combination of logic gates and circuit elements.
[0025] In summary, although the present invention has been disclosed as above in preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various changes without departing from the spirit and scope of the present invention. And retouching, therefore, the protection scope of the present invention should be subject to the scope of the claims.
