The function of feed servo is evaluated with improve measure

The means of two kinds of control that annulus of speed of commutator of silicon controlled rectifier of SCR of transistor of power of IGBT GTR GTR of module of intelligence of power of IPM of module of intelligence of power of IPM of 500 corresponding circuit often uses ≤ of 250 of ≤ of 100 of ≤ of 50 of 5 ≤ to analyse rate system, it is voltaic annulus approximately 1; brings to bear on as a result of the axial end of servo electric machinery laden, so the dynamic character of servo suffers damp and inertial and laden effect. To improve dynamic performance of the system, PID algorithm is the method that often uses on the project, speed annulus often uses have PI and IP means of two kinds of control. Substantially, PI and IP are scale, integral relation. But the order that PI control software handles is first scale, hind integral, be emphasized at scale; and the order that IP control software handles is first integral, hind scale, emphasize at integral. LPI control: Graph 2 control for scale integral, among them K2 is scale gain, k1 is integral gain, KT is coefficient of electric machinery torsion, j is the inertia on axis of servo electric machinery. The PI on the structure emphasizes proportional concern more. Consequently, the system is in after receiving speed to dictate, compare the torsion that short time increased, PI control agrees with systematic machinery tigidity is low, gap is bigger, it is not quite good to answer function, the large scale computer that requirement system catchs up with quickly fetterses, can increase K2 at this moment, reduce K1. If tall mechanical need improves tigidity,start character, also can carry out PI control. Graph 2 PI controls LIP control: Graph 3 control for integral scale, among them K1 is integral gain, k2 is scale gain. KT is coefficient of electric machinery torsion. The IP on the structure emphasizes integral concern. Consequently, machinery begins starting meeting to have certain delay, the system compares stability to start. Accordingly, IP control basically is used in stable to starting a requirement system, for instance, some machinery is tigidity tall, answer sharp small-sized machine, to increase pair of disturbing damp and make start stability, can use IP control, increase K1 of speed annulus gain appropriately at the same time. The analysis of control of graph 3 IP from above and relevant frequency character computation can get: PI has bigger high frequency gain, rose to answer a gender consequently. Photograph frequency is characteristic: PI falls inside frequency domain limits be close to 90 ° ; and IP drops be close to 180 ° PI control is consequently stabler; PI and IP are both fight disturb character is basic and identical. Time of speed annulus sampling: The 2-3 that chooses time of voltaic annulus sampling times OK. Current, the sampling cycle of servo is like a watch about 2: Express 2 servo the annulus of position of annulus of speed of annulus of sampling cycle electric current of 3 annulus 31.

25-125 μ S 62.

5-500 μ S 0.

After 1ms-4ms was analysing speed annulus, have a look at voltaic annulus again, also adopt the structure of PI or IP commonly, analytic method is same also. Besides the structure of PI and IP, the method that also uses regulator of referenced model PI sometimes undertakes compensating. The inertia that laden inertia moves the inertia on axis of characteristic influence servo electric machinery to include electric machinery and load to servo two parts. Above is the circumstance that takes no account of laden inertia to the analysis of speed annulus. Laden inertia is affected directly make a frequency character of speed annulus and photograph frequency characteristic addle. Say commonly, inertia is bigger, use character worse. From the graph 2 ～ pursue 3 see, laden inertia is right of servo use character influential. The 3 ～ that choose laden inertia to not be more than electric machinery inertia commonly 5 times. Character of positional pilot trends pursues operating ring of 4 servo position simplifies analyse above graph course, it is when speed gain is bigger, speed annulus is 1; approximately if the graph is shown 4 times,then the position is controlled. Can regard its open loop as an integral link. Its closed circuit is first-order and inertial link, time constant is a graph 5 in the reciprocal of positional gain Kp. The size of Kp and mechanical load performance have very big concern. Kp is bigger, answer faster. ＝ of Kp of general and large machine tool 20 ～ 40/s, kp=30-60/s of medium, Bench Machine Tool, improve of systematic performance ceaselessly as control, in high speed and high spirit system, through improving voltaic annulus character, increase speed annulus gain, eliminate the step such as mechanical resonance dot, kp can be more than 100/s. Graph 5 feed servo simplifies the servo of the machine tool of relation numerical control of graph system top speed and positional resolution is system of pilot of a figure shift buy, in speed of the biggest output changeless circumstance falls, its position resolution is higher, taller to systematic requirement. Go to the lavatory for the analysis, the gain that establishs annulus of systematic electric current and speed link is enough big, then, can simplify servo graph for the graph 5; Graph the positional gain after 4 medium Kp simplify for servo graph, its meaning is when the position the system has 1 to detect when unit error, speed V of the system is how old. Namely ε of Kp ＝ V/ (2) in type (in 2) , when positional gain changeless, when systematic error is the biggest, its output speed also is the biggest Vmax, if positional controller has N error register of the binary system, so the biggest error is 2N-1, to achieve the biggest Vmax, type (3) is indispensible get satisfaction. Kp(2N-1) ≥ Vmax (3) Vmax heals big, in the circumstance with changeless Kp, the digit of N heals big; system also heals complex. Set 2N>>1, so: Lg(Vmax/Kp)/lg2 (4) of N ≥ for example, design of some machine tool asks resolution is 1nm, the oldest rate is 1m/min=109nm/min, quite 16.

7 × 106pps, positional gain is 100/s, according to type (4) , the error register talent that needs 18 above satisfies index to ask. If positional gain is 25/s, the error register talent that needs 20 above satisfies index to ask. Gain is smaller, what need digit bigger. Electronic gear is compared those who consider input and output unit is different, simplify the feed servo of numerical control machine tool into the graph 5, among them C, d is an instruction respectively unit and detect of the unit times add than. R2 is the smallest mobile unit, m2 is detect unit, r1 is increment of the smallest input, or instruction unit;M1 is servo electric machinery the pulse number; of PC sets the coder when every turn servo electric machinery every turn quite machine tool shift is L, pass C, the coefficient of D alternates, can reach: R1/C ＝ R2 (5) M2 of ＝ of L/M1 × D (6) as a result of R2 ＝ M2, so C/D=R1 × M1/L (7) C/D calls electronic gear to change C than; , d can make servo attainable when the input of increment of same the smallest input differ to detect smally greatly the output of the unit. For example, increment of the smallest input is 1 μ M, detect the unit is 0.

1 μ M, c=10, l=5mm, m1=10000p/r, so D=5. The improvement of servo measure imitate servo needs to increase a lot of additional hardware ability to improve performance. But the resource that can pass software algorithm and communication interface very easily to digital servo increases function and improve performance. For instance: Control of the make a present of before control of make a present of is used before is a kind reduce stable state effectively to follow the method of the error. It is control of a kind of compensation constitutionally. The make a present of before the position that uses digital servo controls algorithm, can reduce lag of positional annulus pilot. After the make a present of before increasing, follow error from type (2) turns into type (8) . E ＝ V/[KP/(1 - A)] (8) among them; of coefficient of the make a present of before A is to reduce the vibration when high speed, still can increase the make a present of before speed to control. Of core structure improve annulus of L electric current to increase " 1/2 PI " control: When laden small electric current, voltaic annulus has; of PI pilot character to become when laden big electric current, it has IP pilot character however, such, the electric current that because big electric current is caused,can reduce exceeds tone, in order to satisfy control of annulus of buy of two-step of; L of need of pilot of high speed expensive precision work: In the treatment on the machine that has large space, stability should is when half closed circuit works, but when making closed circuit possible vibration. For this, adopt; of method of two-step buy pilot to should transfer when the process, the system is in the job below half closed circuit, when fixed position, the system is in damp of vibration of; L of the job below complete closed circuit to control: System of positional closed circuit applies the coder on electric machinery axis to regard speed as feedback sometimes, and use detached type coder to regard the position as feedback; When adding decelerate, the concatenate likelihood between electric machinery and machinery becomes bad, make the speed of mechanical speed and electric machinery is a bit different, this very difficult control is rigid. For this, established oscillatory damp to control segment, it feedbacks the rate difference between electric machinery and machinery to torsion to dictate in order to reduce observation of mechanical oscillatory; L implement function: For instance, use software estimation to control state, build condition observation implement. It can use electric current of estimation electric machinery, speed to eliminate mechanical oscillation in order to identify blame expectation electric current and control. Digital filter is in digital servo, often use digital filter the resonance with purify machinery. This kind of filter has the following kinds: Low connect filter, all sorts of filter that take block. Nonlinear compensation is compensated like pitch, retrorse compensation. Because the last word shows system of acting numerical control to use technology of communication number servo, the performance that because this is OK,improves servo through software algorithm and increase a function. But the basic function to servo is to design numerical control system to should master above all. It includes static character, move characteristic, fast compare with the relation of resolution and electronic gear etc. CNC Milling CNC Machining