[0001]The present invention is to vector control in the dq-axis rotating coordinate system driving the 3-phase brushless motor, Xu gradually switching an instantaneous conditional branch switching (software according to the function a plurality of dead time compensation value under a predetermined condition is corrected by varying the switching, to improve the steering performance on the possibility and the electric power steering system an assist control without smooth steering sound. also, regarding high-performance electric power steering apparatus in consideration of the temperature compensation. BACKGROUND [0002] 　Steering assist force by the rotation force of the motor to a steering mechanism of a vehicle electric power steering apparatus which provides (assist force) (EPS) is the driving force of the motor as an actuator, a transmission mechanism such as gears or a belt via reduction gear the, so as to impart a steering assist force to a steering shaft or a rack shaft. Such conventional electric power steering apparatus, in order to accurately generate a torque of the steering assist force, and performs a feedback control of a motor current. The feedback control is the difference between the steering assist command value (current command value) and the motor current detection value to adjust the voltage applied to the motor so as to reduce, adjustment of the voltage applied to the motor, generally a PWM (Pulse Width modulation) is performed by adjustment of the control of the Duty. [0003] 　To describe the general construction of an electric power steering apparatus shown in FIG. 1, column shaft of the handle 1 (steering shaft, the steering wheel shaft) 2 is a reduction gear 3, universal joints 4a and 4b, a pinion rack mechanism 5, tie rods 6a, through 6b, it is connected further hub unit 7a, via 7b steering wheels 8L, the 8R. In addition, the column shaft 2, a steering angle sensor 14 for detecting a steering angle of the steering wheel 1 theta, a torque sensor 10 for detecting is provided a steering torque Th of the steering wheel 1, to assist the steering force of the steering wheel 1 motor 20 is connected to the column shaft 2 via the reduction gear 3. The control unit (ECU) 30 for controlling the electric power steering apparatus, the electric power from the battery 13 is supplied, the ignition key signal is inputted through the ignition key 11. Control unit 30 performs the calculation of the assist (steering assist) command current command value based on the vehicle speed Vs detected by the steering torque Th and the vehicle speed sensor 12 detected by the torque sensor 10, the calculated current command value controlling the current supplied to the motor 20 by the voltage control command value Vref subjected to compensation for the. Steering angle sensor 14 is not mandatory and may not be disposed, may be from the rotation sensor such as a resolver connected to the motor 20 to obtain the θ steering angle (motor rotation angle). [0004] 　The control unit 30, CAN (Controller Area Network) 40 for exchanging various kinds of information of the vehicle and is connected, the vehicle speed Vs is also possible to receive from CAN40. Further, the control unit 30, communications other than CAN40, an analog / digital signal, even non CAN41 for exchanging radio waves connectable. [0005] 　In such an electric power steering apparatus, the control unit 30 is mainly composed of a CPU (Central Processing Unit) (MPU (Micro Processor Unit) or MCU (including Micro Controller Unit), etc.), a program in the CPU When showing the general functions performed has a configuration as shown in FIG. 2, for example. [0006] 　To explain the function and operation of the control unit 30 with reference to FIG. 2, the vehicle speed Vs from the steering torque Th and the vehicle speed sensor 12 from the torque sensor 10 is inputted to the steering assist command value calculating section 31, the steering assist command value calculation part 31 calculates the steering assist command value Iref1 using an assist map or the like based on the steering torque Th and the vehicle speed Vs. Limiting calculated steering assist command value Iref1 in the addition unit 32A, is added to the compensation signal CM from the compensator 34 to improve the characteristics, the steering assist command value Iref2 that are subject to the maximum value by the current limiting unit 33 is the maximum value the current command value is limited to Irefm is inputted to the subtraction unit 32B, is subtracted and the motor current detection value Im. [0007] 　A subtraction result of the subtraction unit 32B deviation ΔI (= Irefm-Im) is a current control such as PI (proportional integration) in the PI control unit 35, current controlled voltage control command value Vref is the modulation signal (triangular wave carrier ) are inputted to the PWM controller 36 along with CF is calculated the Duty command value to PWM drive the motor 20 via the inverter 37 with the PWM signal which is calculated the Duty command value. Motor current value Im of the motor 20 is detected by a motor current detector 38, is inputted to the subtraction unit 32B by feedback. [0008] 　Compensation unit 34 adds the inertia compensation value 342 by an adder 344 to detect or estimated self aligning torque (SAT), by adding the convergence control value 341 in further addition unit 345 to the addition result, the addition the results were input to the addition unit 32A as the compensation signal CM, implementing the performance improvement. [0009] 　Recently, with the actuator of the electric power steering apparatus is a three-phase brushless motor has become a mainstream, because the electric power steering system is a vehicle products, wide operating temperature range, the inverter home electronics for driving the motor in terms of fail-safe products in comparison with the general industrial use to the representative, it is necessary to increase the dead time (industrial equipment VR1), to maintain a constant value DTCa2 a predetermined voltage VR2 higher characteristics it is. Compensation amount upper limit value DTCa is is inputted to the contact a1A and comparison unit 255 of the switching unit 252, is input to the inverting section 254. Moreover, phase loss voltage PLB (Vloss_u, Vloss_v, Vloss_w) is is inputted to the comparator 255 and 256 are inputted to the contact b1A switching unit 252. The output -DTCa the inverting unit 254 is input to the contact a2A the switching unit 253. Contact a1A and b1A switching unit 252 is switched based on the comparison result CP1 of the comparison unit 255, the contact a2A and b2A switching unit 253 is switched based on the comparison result CP2 of the comparator 256. [0054] 　Comparing unit 255 compares the compensation amount upper limit value DTCa and phase loss voltage PLB, switches the contacts a1A and b1A switching unit 252 according to the following equation 8. The comparison unit 256 compares the compensation amount upper limit value -DTCa and phase loss voltage PLB, switches the contacts a2A and b2A switching unit 253 according to the following equation (9). [0055] 　(8) When the phase loss voltage PLB ≧ compensation amount upper limit value DTCA, contact a1A switching unit 252 is turned ON when the phase loss voltage PLB Icm1), is a characteristic to maintain a constant gain Gcc2 a predetermined current Icm2 more. The predetermined current Icm1 may be 0 [A]. [0062] 　Compensation code estimator 402 with respect to the current command value Icm inputted, outputs a compensation code SN1 positive hysteresis characteristic shown in FIG. 15 (A) and (B) (+1) or negative (-1). Although the current command value Icm estimates the compensation code SN1 as a reference point to the zero crossing, and has a hysteresis characteristic for the chattering suppressing. Estimated compensation code SN1 is input to the multiplier 403. [0063] 　Current command value sensitive gain Gc from the current command value sensitive gain unit 450 is input to the multiplier 403, the multiplication unit 403 outputs a current command value sensitive gain Gcs obtained by multiplying the compensation code SN1 (= Gc × SN1). Current command value sensitive gain Gcs is input to the multiplier 404d and 404q. [0064] 　Since the optimum dead time compensation amount is changed according to the inverter application voltage VR, calculates a dead time compensation amount corresponding to the inverter application voltage VR, so that variable. Inverter application voltage sensitive gain calculating unit 420 for outputting a voltage sensitive gain Gv by entering the inverter application voltage VR is as shown in FIG. 16, the inverter application voltage VR is limited to the positive and negative maximum value at the input limiting unit 421, the maximum inverter application voltage VRl a restricted value is input to the inverter application voltage / time compensation gain conversion table 422. Characteristics of the inverter application voltage / time compensation gain conversion table 422, for example, as in Figure 17. An inverter application voltage 9.0 inflection point [V] and 15.0 [V], the voltage sensitive gain "0.7" and "1.2" is an example, can be appropriately changed. The calculated voltage sensitive gain Gv is multiplied unit 431U, 431V, is input to 431W. [0065] 　Or early dead time compensation timing by the motor rotation speed omega, if you want to slow down, and a phase adjustment unit 410 for the function to calculate the adjustment angle in accordance with the motor rotation speed omega. Phase adjustment section 410, if the advance angle control is a characteristic as shown in FIG. 18, the calculated phase adjustment angle Δθ is input to the adder 421, is added to the motor rotational angle θ that is detected. Motor rotation angle θm which is the addition result of the adder 421 (= θ + Δθ), the angle - dead time (DT) compensation value function unit 430U, 430V, is input to the 430 W, the three-phase AC / dq axis conversion section 440 It is input. [0066] 　Angle - dead time compensation value function unit 430U, 430V, 430W, as shown in detail in FIG. 19, the phase adjusted motor rotation angle .theta.m, 120 in the range of electrical angle 0 ~ 359 [deg] [deg] each phase-shifted rectangular wave of each phase dead time reference compensation value UDT, Vdt, and outputs a Wdt. Dead time compensation value angle function unit 430U, 430V, 430W is the dead time compensation value required at three phases as a function depending on the angle, calculated on real time ECU, the dead time reference compensation value UDT, Vdt, Wdt to output. Angle function of the dead time reference compensation value is different depending on the characteristics of the dead time of the ECU. [0067] 　Dead time reference compensation value Udt, Vdt, Wdt each multiplication unit 431U, is input 431V, to 431W, is multiplied by the voltage sensitive gain Gc. Voltage sensitive gain Gc multiplied three phase dead time compensation value Udtc (= Gc · UDT), Vdtc (= Gc · Vdt), WDTC (= Gc · Wdt) is inputted to the 3-phase AC / dq axis conversion section 440 It is. 3-phase AC / dq axis conversion section 440 in synchronization with the motor rotation angle .theta.m, 3-phase dead time compensation value Udtc, Vdtc, compensation value dq axes of two phases WDTC v da * and v qa * converted to to. Compensation value v da * and v qa * are input to respective multipliers portion 404d and 404q, it is multiplied by the current command value sensitive gain Gcs. Multiplication result of the multiplying unit 404d and 404q are dq-axis compensation value CdB and CQB, compensation values CdB and CQB is inputted to the switching section 541 and 542, respectively compensation value changeover portion 500. [0068] 　Then, the dead time compensator for (C) 600 (Example 1) will be described. [0069] 　Dead time compensation unit 600 as shown in FIG. 20, the addition unit 601, the multiplication unit 602, an inverter application voltage sensitive compensation amount calculating section 610,3 phase current command value model 620, the phase current compensation code estimating unit 621, the phase adjusting unit It is composed of 630,3-phase AC / dq axis conversion section 640. Motor rotational angle θ is inputted to the adder 601, the motor rotation speed ω is input to the phase adjuster 630. The inverter application voltage VR is input to an inverter application voltage sensitive compensation amount calculation unit 610, the motor rotation angle θm after the phase adjustment calculated by the adder 601 is input to the 3-phase current command value model 620. [0070] 　Or early dead time compensation timing by the motor rotation speed omega, if you want to slow down, and a phase adjustment unit 630 for the function to calculate the adjustment angle in accordance with the motor rotation speed omega. Phase adjustment section 630, in the case of the advance angle control is a characteristic as shown in FIG. 18, the calculated phase adjustment angle Δθ is input to the adder 601, it is added to the motor rotational angle θ that is detected. Motor rotation angle θm after the phase adjustment is the addition result of the adder 601 (= θ + Δθ) is inputted to the 3-phase current command value model 620 is input to the 3-phase AC / dq axis conversion section 640. [0071] 　Optimum dead time compensation amount because changes in accordance with the inverter application voltage VR, calculates a dead time compensation amount DTC corresponding to the inverter application voltage VR, so that variable. Inverter application voltage sensitive compensation amount calculation unit 610 for outputting a dead time compensation amount DTC enter the inverter application voltage VR is as shown in FIG. 21, the inverter application voltage VR is limited to the positive and negative maximum value at the input limiting unit 611 , the inverter application voltage VRl that is limited to the maximum value is input to the inverter application voltage / dead time compensation amount conversion table 612. Characteristics of the inverter application voltage / dead time compensation amount conversion table 612, for example, as in Figure 22. That is, a certain dead time compensation amount DTC1 to a predetermined inverter applied voltage VR1, increases linearly (or non-linear) from a predetermined inverter application voltage VR1 to a predetermined inverter application voltage VR2 (> VR1), at a predetermined inverter application voltage VR2 higher is a characteristic which outputs a constant dead time compensation amount DTC2. [0072] 　d-axis current command value i d * and the q-axis current command value i q * along with the motor rotation angle .theta.m, is inputted to the 3-phase current command value model 620. 3-phase current command value model 620, dq axis current command value i d * and i q * , the motor rotation angle .theta.m, 3-phase current model 120 [deg] by the phase-shifted sine wave as shown in FIG. 23 a command value Icm is calculated by the calculation or table. 3-phase current model command value Icm is different by motor type. [0073] 　3-phase current model command value Icm is input to the phase current compensation code estimator 621. Against 3-phase current model command value Icm is the phase current compensation code estimator 621 is input, the compensation code SN2 positive hysteresis characteristic shown in FIG. 24 (A) and (B) (+1) or negative (-1) to output. 3-phase current model command value Icm estimates the compensation code SN2 based on the point of zero crossing, but a hysteresis characteristic for the chattering suppressing. Estimated compensation code SN2 are input to the multiplier 602. [0074] 　Dead time compensation amount DTC from the inverter application voltage sensitive compensation amount calculation unit 610 is input to the multiplier 602, the multiplication unit 602 outputs the dead time compensation amount DTCa obtained by multiplying the compensation code SN2 (= DTC × SN2). Dead time compensation amount DTCa is inputted to the 3-phase AC / dq axis conversion section 640, three-phase AC / dq axis conversion section 640 outputs the compensation value CdC and CqC the dq-axis in synchronization with the motor rotation angle .theta.m. Each compensation value CdC and CqC is inputted to the switching section 541 and 542 of the compensation value switching section 500. [0075] 　Switch switching determination unit 510 of the compensation value switching section 500 is as shown in FIG. 25, d-axis current command value i d * and outputs a determination flag DF1 when becomes close to zero (e.g., 0.1 [A] or less) and a zero determination unit 511. Further, q-axis current command value i q * of the absolute value | i q * and the absolute value unit 512 to obtain the absolute value | | i q * along with outputs a determination flag DF2 when a predetermined threshold value TH1 or more | , a threshold unit 513 having a hysteresis characteristic, the absolute value of the motor speed omega | omega | absolute value unit 514 to obtain the absolute value | with outputs a determination flag DF3 when a predetermined threshold value TH2 or more | omega , and a threshold portion 515 having a hysteresis characteristic. Determination flag DF1 ~ DF3 is inputted to the switching condition determination unit 516, and outputs a switching determination flag SF1 when determination flag DF1 ~ DF3 is input all. For example determination flag DF1 = "L", the determination flag DF2 = "H", when the determination flag DF3 = "H", the switching condition determination unit 516 outputs the "H" switching determination flag SF1 =. "H" and "L" indicates an example of a logic value "H" and "L" may be reversed. [0076] 　During OFF the switching determination flag SF1 is not output (e.g. SF1 = "L"), the contact of the switch switching unit 541 and 542 of the conditional branch 540, as shown in FIG. 5 is turned a1 and a2, compensation values ​​CdB and CqB from the dead time compensator (B) 400 is output as respective compensation values ​​Cd and Cq. Then, at the time of ON of the switching determination flag SF1 is output (e.g., SF1 = "H"), the contact of the switch switching unit 541 and 542 are switched from each a1 and a2 to b1 and b2. As a result, the compensation value CdC and CqC from the dead time compensator (C) 600 is output as respective compensation values ​​Cd and Cq. Each compensation value Cd and Cq from conditional branching unit 540, is input to the multiplier 552 and 554 of Xu Hensetsu section 550. [0077] 　Gradually changing the switching determination unit 520 the steering assist command value iqref a changeover condition, has a dead zone with respect to the input signal, the determination condition having hysteresis outputs an UP / DOWN judgment flag SF2. Its configuration example is 26, the steering assist command value iqref is the processing of the dead zone is entered to the dead zone portion 521 (e.g., ± 0.5 [A]), dead zone processing steering assist command value iqref-d is It is input to the absolute value unit 522, the absolute value of the absolute value unit 522 | iqref-d | is limited to upper and lower limit values ​​by the limiter 523. Steering assist command value iqref-t that is limited to the upper and lower limit values ​​are input to the threshold unit 524 having a hysteresis characteristic, the threshold unit 524 outputs the UP / DOWN judgment flag SF2 based on the magnitude relationship between the predetermined threshold value. UP / DOWN judgment flag SF2 is input to the gradual change rate calculating section 530. [0078] 　Dead zone 521 in the vicinity of on-center of the handle, external factors since the signal fluctuates by (the state of the road surface (gravel, etc. slopes, etc.) and vehicle body vibration) is provided in order to avoid these, dead band section 521 to remove the vibrational components of the steering assist command value iqref to enter. Further, hysteresis characteristics of the threshold unit 524 has a function of preventing the chattering after the dead zone, to stabilize the output. [0079] 　Gradually changing rate calculating section 530 is as shown in FIG. 27 for example, ON of UP / DOWN judgment flag SF2 (e.g. SF2 = "H"), is switched contacts am and bm by OFF (e.g. SF2 = "L") a switch 531, the count UP value 532 is input to the contact am, count DOWN value 533 is input to the contact bm. For example, during ON UP / DOWN judgment flag SF2 is input, the count UP value 532 is connected to the contact am (eg + 0.5%) is output from the switch 531, UP / DOWN judgment flag SF2 is not input no is OFF is switched to the contact bm, count DOWN value 533 (e.g., -0.5%) is output from the switch 531. The output of the switch 531 is input to the adder 534, the added value is the count value limiting section (0-100%) 535 limits the maximum value, is outputted as a gradual change ratio RtBC (%), the subtraction unit 537 is subtracted input, the holding unit (Z -1 is input to the adder 534 via) 536. Gradual change ratio RtBC is inputted to the subtraction unit 537 outputs a value obtained by subtracting from 100% fixed as gradual change ratio RTA (%). As a result, gradual change ratio RtA varies linearly from 100% to 0%, the gradual change ratio RtBC varies linearly from 0% to 100%, gradual change ratio RtA and characteristics as indicated by a solid line in FIG. 28 RtBC can be obtained. Incidentally, there are always the following relationship number 10 between the gradual change ratio RtA and RtBC, gradual change ratio RtA and RtBC are input to Xu Hensetsu section 550. [0080] 　(Number 10) 　RTA (%) + RtBC (%) = 100% 　Figure instant t of 28 0 ~ t 1 but is the switching time by gradually changing the switching, can vary the switching time by changing the size of the count value . For example the count UP value 532 + 0.5%, by the count DOWN value 533 to such -2%, slow switching dead time compensation B from the dead time compensation A, switching of the dead time compensation A from the dead time compensation B You can vary the switching time by fast gradual change nonlinearly. It can also increase the size of the count UP values 532 and count DOWN value 533, by or reduced, so adjust the speed of the switched. claims Calculates a dq axis steering assist command value based on at least the steering torque, the steering assist calculates the dq-axis current command value from the command value, the 3 phases computed dq-axis voltage command value from the dq-axis current command value converted into Duty command value, a 3-phase brushless motor by a PWM control inverter drive control, the electric power steering apparatus of a vector control method for imparting assist torque to a steering mechanism of a vehicle, each phase motor terminal voltage and the Duty command compensation performing a compensation function 1 for dead time compensation a based on the value, the compensation function 2 for dead time compensation B based on the steering assist command value, the dead time compensation C on the basis of the dq-axis current command value ; and a function 3, the compensation function 1, wherein the compensation function 2, wherein performing the switching of the compensation function 3 with conditional branching and gradually changing the switching by software d Axis dead time compensation value calculated, the electric power steering apparatus characterized by compensating the dq-axis voltage command value in the dq-axis dead time compensation value. [Requested item 2] The use of gradual change switching when the compensation amount switching 換差 amount of time of switching is small, the electric power steering apparatus according to claim 1 using said conditional branch if the speed of the switching timing is required. [Requested item 3] The compensation function 1, 2 and 3 are both further motor rotation angle, the electric power steering apparatus according to the motor rotation speed and the inverter application voltage to claim 1 or 2 is used for the calculation. [Requested item 4] The inverter or temperature detector is provided for detecting the temperature around the inverter, the dead time compensation B and the dead time compensation C of deadtime correction is carried out so since with the claims 1 to 3 is based on the temperature the electric power steering apparatus according to any one. [Requested item 5] Calculates a dq axis steering assist command value based on at least the steering torque, the steering assist calculates the dq-axis current command value from the command value, the 3 phases computed dq-axis voltage command value from the dq-axis current command value converted into Duty command value, and drives and controls the three-phase brushless motor by an inverter of PWM control, the electric power steering apparatus of a vector control method for imparting assist torque to a steering mechanism of a vehicle, each phase motor terminal voltage, the Duty command value, the motor rotation angle, a dead time compensation unit a for calculating a compensation value CA based on the motor rotation speed and the inverter application voltage, the steering assist command value, the motor rotation angle, the motor rotation speed and the inverter application voltage a dead time compensation unit B for calculating the compensation value CB based, the dq-axis current command value, the motor rotation angle, the motor Rolling speed and includes a dead time compensation unit C for computing a compensation value CC on the basis of the inverter applied voltage, the compensation value CA, the compensation value CB, and inputs the compensation value CC, the steering as switching condition assist command value, the dq-axis current command value and inputs the motor rotation speed, determined the compensation value CA by the conditions, CB, CC dq axis dead time by performing switching at conditional branch and gradual change switching by software It includes a compensation value switching section for calculating a compensation value, the electric power steering apparatus characterized by compensating the dq-axis voltage command value in the dq-axis dead time compensation value. [Requested item 6] The compensation value changeover portion is performed switching determination by entering the dq-axis current command value and the motor rotational speed, and switches the switching determination unit for outputting a switching determination flag, and inputs the compensation value CB and CC, the a conditional branch portion for outputting a dq-axis compensation value CD by the conditional branch based on the switching determination flag, determines the gradual-change switching based on the steering assist command value, and a gradually changing portion for calculating a gradual change ratio, the enter the compensation value CA and the dq-axis compensation value CD, and Xu Hensetsu section calculates and outputs the dq axis dead time compensation value in the gradual-change ratio, an electric according to claim 5, in being configured power steering apparatus. [Requested item 7] The gradually changing portion is, and the steering assist command value to determine the gradual change switching based on the UP-DOWN decision flag gradual change switching determination unit that outputs, the gradual change ratio on the basis of the UP-DOWN determination flag and gradually changing rate calculating section calculates, in the electric power steering apparatus according to claim 6 is configured. [Requested item 8] The gradual change ratio, a gradual change ratio RA for the compensation value CA, sequence by the gradual change ratio RBC for the compensation value CB and CC, the Xu Hensetsu section is, the compensation value CA and the gradual-change ratio adding a first multiplication section for multiplying the RA, and a second multiplication unit for multiplying the dq-axis compensation value CD and the gradual change ratio RBC, the multiplication result of the multiplication result of the first multiplication portion and the second multiplication section to an electric power steering apparatus according to claim 7, which is constituted by an adder which outputs the dq axis dead time compensation value. [Requested item 9] Calculates a dq axis steering assist command value based on at least the steering torque, the steering assist calculates the dq-axis current command value from the command value, the 3 phases computed dq-axis voltage command value from the dq-axis current command value converted into Duty command value, a 3-phase brushless motor by a PWM control inverter drive control, the electric power steering apparatus of a vector control method for imparting assist torque to a steering mechanism of a vehicle, detecting a temperature of the inverter or near the inverter a temperature detection unit that, each phase motor terminal voltage, the Duty command value, the motor rotation angle, a dead time compensation unit a for calculating a compensation value CA based on the motor rotation speed and the inverter application voltage, the steering assist command value, the motor rotation angle, the motor rotation speed, to calculating the compensation value CB on the basis of the inverter applied voltage and the temperature A dead time compensation section B, the dq-axis current command value, the motor rotation angle, the motor rotational speed, and the dead time compensation unit C for computing a compensation value CC on the basis of the inverter applied voltage and the temperature, the compensation value CA, temperature corrected the compensation value CB, and inputs the compensation value CC which is temperature corrected, the steering assist command value, and inputs the dq-axis current command value and the motor rotation speed as a switching condition, it is determined a conditional branch the compensation value CA, CB, the switching of the CC by software using conditions, performed by the steering assist command value and gradually changing the switching based on the motor rotational speed compensation value changeover portion calculates the dq axis dead time compensation value When, the provided, the dq-axis voltage command value, an electric power steering, characterized in that to compensate a temperature-corrected the dq axis dead time compensation value apparatus. [Requested item 10] The gradual change switch, calculates a gradual change switching determination unit for outputting a switching count value by inputting the steering assist command value and the motor rotation speed, the gradual-change switching 換比 rate by inputting the switching count gradual change the electric power steering apparatus according to claim 9, which is constituted by the ratio calculation unit. [Requested item 11] The gradual change switching determining unit, the steering assist current factor unit for outputting a q-axis current factor SWITCH COUNT UP / DOWN value based on the command value, the rotational speed factors SWITCH COUNT UP / DOWN value based on the motor rotational speed a rotational speed factor unit for outputting, and a the q-axis current factor SWITCH cOUNT UP / DOWN value and the rotational speed factors SWITCH cOUNT UP / DOWN value adding unit that adds and outputs the switching count value the electric power steering apparatus according to claim 10 [Requested item 12] The gradual change rate calculating section is, the switching count value and the count value limiting unit for inputting the added value of the previous value of the gradual change ratio 2, subtracted to gradual change ratio of the gradual-change ratio of 2 to 100% of the fixed value the electric power steering apparatus according to claim 10 or 11 is composed of a subtraction unit for outputting a 1. [Requested item 13] Calculates a dq axis steering assist command value based on at least the steering torque, the steering assist calculates the dq-axis current command value from the command value, the 3 phases computed dq-axis voltage command value from the dq-axis current command value converted into Duty command value, a 3-phase brushless motor by a PWM control inverter drive control, the electric power steering apparatus of a vector control method for imparting assist torque to a steering mechanism of a vehicle, each phase motor terminal voltage and the Duty command a compensation function 1 for dead time compensation a based on the value, the compensation function 2 for dead time compensation B based on the steering assist command value, compensating for performing the dead time compensation C on the basis of the dq-axis current command value and functionality 3, comprises a, the compensation function 1, wherein the compensation function 2, a switching of the compensation function 3, the steering assist finger conditional branch in software Performs in a gradual change switching based on the value and the motor rotation speed, performs the gradual change switching nonlinear function calculates the dq axis dead time compensation value after the conditional branch and the gradual change switching, the dq axis dead an electric power steering apparatus characterized by compensating the dq-axis voltage command value at time compensation value. [Requested item 14] The nonlinear function, the electric power steering apparatus according to claim 13 is a configuration using a gradual change ratio characteristic conversion table of non-linear characteristics in the subsequent stage of the count value limiting section after switching the count UP value and the count DOWN value. [Requested item 15] Said nonlinear function, is composed of a count UP value calculation processing unit of the nonlinear and count DOWN value processing unit which is sensitive to motor rotation speed, as the output switching of the count UP value calculation processing unit and said count DOWN value processing unit and it has an electric power steering apparatus according to claim 13. [Requested item 16] Further, the temperature detecting unit for detecting the temperature in the vicinity of the inverter or the inverter is provided, the electric power according to any one of claims 13 to 15 adapted to correct the compensation function 2 and 3 on the basis of the temperature steering apparatus.