摘要:
A method for playing a recording medium, in particular an optical storage disc, used to access titles more quickly. Stored in a run-in area of the recording medium is at least one address area that includes at least one address of a beginning of a title stored on the recording medium. The recording medium is played in a player having a read device. When the at least one address area is read out, the at least one address of a title beginning is converted to a start time of exactly one time unit and stored in a memory, with the start time corresponding approximately to the playing time of the recording medium up to the addressed title beginning. To position the read device at the beginning of the title, the track jump time is calculated directly from the corresponding start time stored in the memory.
摘要:
During operation of a 3 phase BLDC motor it is driven by use of a PWM waveform applied to one of the driven phase (curve a). The other driven phase is connected thereto but no driving signal is applied (curve b). The third phase is left floating (curve c). This allows the back EMF in the third phase to be monitored for the purpose of determining rotor position by detection of zero crossing points. The rapid switching of the PWM pulses causes ringing in the back EMF signal indicated for one pulse by the ringed portions 1 of curve c. The ringing in the back EMF signal introduces inaccuracy into position calculations derived from back EMF signal measurement. In order to reduce this ringing, in the present invention, a reverse pulse is applied to the other driving coil shown (curve b) prior to a PWM on pulse. The reverse pulse has a polarity such that it drives the phase current through the linked coils in a direction opposite to that caused by the PWM on pulse. This reverse pulse reduces the magnitude of the ringing in the back EMF signal.
摘要:
The present invention there is provides a method of determining the rotor position in an electric motor comprising the steps of: superimposing one or more alternating signals on to the driving waveform so as to generate one or more oscillating currents in the stator coils; monitoring the variation in magnitude of the oscillating currents and thereby determining the rotor position. Typically, two alternating signals are applied in opposition so as to have no net effect on the torque applied by the driving waveform. Using this technique rotor position estimation can be obtained at start-up from stand-still and at low to medium speeds. The method can be used in applications where a fast motor start is needed under unknown load conditions and can be used to detect when the rotor has passed a certain position that coincides with the commutation instance.
摘要:
In response to the determination or estimation of a back EMF zero crossing event for the phase, a time T1 is calculated, T1 being representative of the desired absolute maximum value of the phase current. Current samples are taken by the current sampling unit symmetrically centred around T1. The values of the samples CS[1] to CS[10] are then input into the error function to calculate an error function value. The calculated error function value is input to the lead angle control unit which calculates a value for lead_angle. The value of lead_angle is calculated to be the adjustment in phase angle of the driving voltage profile that will minimise the absolute value of the error function. In generating and adjusting the driving voltage profile the driving voltage generation unit takes into account both lead_angle and the output of the position and speed estimation unit. The estimated motor speed may be used additionally in an outer speed control loop involving speed controller to adjust the amplitude (AMP) of the effective driving voltage.
摘要:
In response to the determination or estimation of a back EMF zero crossing event for the phase, a time T1 is calculated, T1 being representative of the desired absolute maximum value of the phase current. Current samples are taken by the current sampling unit symmetrically centered around T1. The values of the samples CS[1] to CS[10] are then input into the error function to calculate an error function value. The calculated error function value is input to the lead angle control unit which calculates a value for lead_angle. The value of lead_angle is calculated to be the adjustment in phase angle of the driving voltage profile that will minimize the absolute value of the error function. In generating and adjusting the driving voltage profile the driving voltage generation unit takes into account both lead_angle and the output of the position and speed estimation unit. The estimated motor speed may be used additionally in an outer speed control loop involving speed controller to adjust the amplitude (AMP) of the effective driving voltage.
摘要:
In a three phase BLDC motor the rotor position is monitored by detecting the zero crossing points of the induced back EMF signals BEMF_U, BEMF_V, BEMF_W in the phase windings U, V, W. As they are illustrated, the back EMF signals are substantially sinusoidal but they may in other situations be substantially trapezoidal. The three back EMF signals are 120° out of phase with each other. In order to accurately monitor the back EMF in a phase winding, the driving waveform for each phase U, V, W includes an undriven period P close to the expected zero crossing point. The period P can be a preset part of the driving waveform or can be an interruption of the normal driving waveform in response to suitable interrupt signals. In order to determine the zero crossing points of each back EMF signal, two (or more) samples of the back EMF are taken during the undriven period P and used to interpolate the back EMF signal to determine the zero crossing point.
摘要:
In order to determine the orientation of the rotor of a brushless DC motor 100, a sequence of current pulses may be applied to the stator phases U, V, W by the respective drivers HS0, LS0, HS1, LS1 HS2, LS2. The current generated in the stator phases U, V, W in turn generates a current in a shunt resistor 110. The current in this shunt resistor 110 is monitored by use of a current voltage converter 120 and a comparator 130 to determine when it exceeds a predetermined threshold. The rise time until the threshold current is exceeded is recorded in capture unit 140. A processor unit 150 then calculates a scalar parameter SU, SV, SW for each respective stator phase U, V, W from the recorded rise times associated with each pulse. The orientation of the magnetic axis of the rotor can then be determined by consideration of the scalar parameters SU, SV, SW of each stator phase U, V, W, as the respective rise times of each pulse are determined by the inductive properties of the respective stator phases U, V, W, which in turn are dependent upon the orientation of the rotor.
摘要:
In a three phase BLDC motor the rotor position is monitored by detecting the zero crossing points of the induced back EMF signals BEMF_U, BEMF_V, BEMF_W in the phase windings U, V, W. As they are illustrated, the back EMF signals are substantially sinusoidal but they may in other situations be substantially trapezoidal. The three back EMF signals are 120° out of phase with each other. In order to accurately monitor the back EMF in a phase winding, the driving waveform for each phase U, V, W includes an undriven period P close to the expected zero crossing point. The period P can be a preset part of the driving waveform or can be an interruption of the normal driving waveform in response to suitable interrupt signals. In order to determine the zero crossing points of each back EMF signal, two (or more) samples of the back EMF are taken during the undriven period P and used to interpolate the back EMF signal to determine the zero crossing point.
摘要:
In order to determine the orientation of the rotor of a brushless DC motor 100, a sequence of current pulses may be applied to the stator phases U, V, W by the respective drivers HS0, LS0, HS1, LS1, HS2, LS2. The current generated in the stator phases U, V, W in turn generates a current in a shunt resistor 110. The current in this shunt resistor 110 is monitored by use of a current voltage converter 120 and a comparator 130 to determine when it exceeds a predetermined threshold. The rise time until the threshold current is exceeded is recorded in capture unit 140. A processor unit 150 then calculates a scalar parameter SU, SV, SW for each respective stator phase U, V, W from the recorded rise times associated with each pulse. The orientation of the magnetic axis of the rotor can then be determined by consideration of the scalar parameters SU, SV, SW of each stator phase U, V, W, as the respective rise times of each pulse are determined by the inductive properties of the respective stator phases U, V, W, which in turn are dependent upon the orientation of the rotor.
摘要:
During operation of a 3 phase BLDC motor it is driven by use of a PWM waveform applied to one of the driven phase (curve a). The other driven phase is connected thereto but no driving signal is applied (curve b). The third phase is left floating (curve c). This allows the back EMF in the third phase to be monitored for the purpose of determining rotor position by detection of zero crossing points. The rapid switching of the PWM pulses causes ringing in the back EMF signal indicated for one pulse by the ringed portions 1 of curve c. The ringing in the back EMF signal introduces inaccuracy into position calculations derived from back EMF signal measurement. In order to reduce this ringing, in the present invention, a reverse pulse is applied to the other driving coil shown (curve b) prior to a PWM on pulse. The reverse pulse has a polarity such that it drives the phase current through the linked coils in a direction opposite to that caused by the PWM on pulse. This reverse pulse reduces the magnitude of the ringing in the back EMF signal.