85results about How to "Reduce frequency of adjustment" patented technology

The invention relates to the technical field of switching power supply and discloses a direct current switching power supply parallel system current sharing control method and a control device. The control device comprises a plurality of switching power supply current sharing modules which are connected in parallel and an extreme current selective circuit, wherein load output terminals of a plurality of switching power supply current sharing modules which are connected in parallel are connected with loads, and the extreme current selective terminals of a plurality of switching power supply current sharing modules which are connected in parallel are connected with the extreme current selective circuit. By applying the direct current switching power supply parallel system current sharing control method and control device disclosed by the invention, a direct current switching power supply parallel system can operate normally under the condition that a basic element is in fault, thus the direct current switching power supply parallel system current sharing control method and control device are applicable to a power supply parallel system with redundant structure, and reliability and safety of the a power supply system and loads are improved; and power supply equipment cost is reduced, the aim of current sharing of the parallel system is realized, regulating frequency of a power supply module of the power supply system is reduced, low-frequency oscillation produced by output current is effectively avoided and dynamic response of the system is further improved while no intelligent controller (CPU) or complex programming technology is adopted.

The invention discloses a control method of an air conditioner, and further discloses a control device of the air conditioner, the air conditioner and a readable storage medium. The method comprises the following steps of controlling the air conditioner to run in a refrigeration mode so as to complete condensation and frosting when the air conditioner is in a self-cleaning mode; controlling the air conditioner to run in a heating mode, and acquiring the current coil temperature of a heat exchanger as the first coil temperature; and adjusting the frequency of a compressor and the rotating speedof a fan of the heat exchanger according to the first coil temperature. With the air conditioner, the control method and control device thereof and the readable storage medium, the running stabilityof the compressor can be improved.

The invention provides an event driving based generalized predictive and self-adaptive supply ship navigation direction control method. The method comprises the following steps: first, selecting a discrete event triggering device working in a discrete state; designing a triggering detection function at a variable threshold; when the triggering time approaches, determining by the event triggering device whether the current state satisfies the triggering condition or not through triggering detection function; second, through the low-frequency motion mathematical model of the supply ship, obtaining the controlled autoregressive integrated moving average model of the rudder angle-navigation direction; taking it as a prediction model; and estimating online the parameters of the prediction model through the use of the forgetting factor recursive least squares method; and third, combining with the event-driving trigger to send the state to be controlled to the controller; using the GPC self-adaptive algorithm by the controller to calculate and output the rudder angle control increment and rudder angle control and enabling the supply ship to rapidly accomplish the approaching stage and the parallel stage as well as to maintain the navigation direction tracking in the supply stage. According to the invention, the navigation direction of the supply ship can be controlled at a low expense and the variation of parameters and the environmental impact of the supply system are more robust.

The invention provides current sharing control circuit and control method of double-current sharing buses of a parallel DC switch power supply. The current sharing control circuit comprises N DC switch power supplies which operate in parallel connection, wherein N = 1, 2, and the like; all the DC switch power supplies are connected together through two different common current sharing buses, and each DC switch power supply comprises a DC power supply main circuit, a central processing unit (CPU), a PWM generation circuit, an A / D conversion circuit, a voltage detection circuit, a current detection circuit, a current sharing signal generation circuit, a first current sharing bus and a second current sharing bus. The invention has very good redundancy rate and interference resistance, is beneficial to enhancing the reliability and the safety of a power supply system and load and can reduce the regulating frequency of each power supply, effectively prevent the output current from generating low-frequency oscillation, enhance the work efficiency and the quality of the output voltage of the integral power supply system and better meet the requirements of the load.

The invention discloses a receiving end optical power control system used for fiber vibration sensing. A light emission port of a light source is connected with a light divider through a vibration sensing fiber. A second light division branch of the light divider is connected with an optical path of an optical detector. The optical detector converts light signal intensity into a light intensity simulation electric signal. An amplifier is used for amplifying the light intensity simulation electric signal. An analog-digital converter converts the amplified light intensity simulation electric signal into a digital signal used for representing light intensity. A threshold value judger is used for judging whether the digital signal used for representing light intensity is lower than a normal optical power threshold value, and if yes, an output number is amplified. An optical power adjuster is used for converting the adjusted number into a simulation signal. A driving circuit adjusts the driving current intensity of the light source according to the simulation signal so as to adjust the output optical power of the light source. According to the invention, the system is capable of acquiring relatively stable receiving optical power at the end of the optical detector in a low-cost resonant sensing system.

The invention provides a blast furnace and hot blast stove constant-pressure changing system. The system comprises a blast furnace, a plurality of hot blast stoves and an air blower station, wherein an air blower in the air blower station has a fixed wind pressure control mode and a fixed wind quantity control mode. When a control system of the blast furnace sends a hot blast stove changing signal, the air blower is switched to the fixed wind pressure control mode while when the control system of the blast furnace sends a hot blast stove changing finishing signal, the air blower is switched to the fixed wind quantity control mode. The system has the advantages that the pressures of a cold wind general pipe and a hot wind general pipe in change of the hot blast stoves are maintained stable, the change of the hot blast stoves is ensured smooth, the influence of change of the hot blast stoves on the blast furnace is reduced, and the adjusting frequency of a pressurizing valve is further reduced, so that the stove changing time is shortened. A control program is newly added to operate on the existing upper computer of the control system and existing hardware equipment is fully utilized, so that the system is less in investment and convenient to retrofit.

The invention provides a valve-adjusting method for the optimal opening of an electronic expansion valve. The valve-adjusting method for the optimal opening of the electronic expansion valve is used for adjusting through a method for quickly adjusting the initial opening and finding the optimal opening of a valve body through a return air superheat degree. The valve-adjusting method for the optimal opening of the electronic expansion valve comprises the steps of (1) when a refrigerating device starts running, acquiring running parameters of the refrigerating device; (2) determining the initialopening of the valve body of the electronic expansion valve according to the running parameters; (3) starting a fan, enabling the system pressure to achieve a balance, and after the fan runs for a preset time, starting a compressor; (4) after the compressor runs for a preset time, and detecting a coil temperature and a return air temperature, wherein a difference value between the coil temperature and the return air temperature is the return air superheat degree; and (5) adjusting the opening of the valve body of the electronic expansion valve according to the return air superheat degree.

The invention discloses a method and a device for coordinating the downlink interference of a long term evolution (LTE) system. The method comprises the following steps of: acquiring the quantity demand of a high-power-frequency-band physical resource block (PRB) of a cell group; dynamically setting the high-power-frequency-band PRB of adjacent cells according to the acquired quantity demand of the high-power-frequency-band PRB and pre-configured static high-power-frequency-band PRB of the cell group; and coordinating downlink power, load or switching of an edge user of the current cell according to the quantity demand of the high-power-frequency-band PRB of the cell group, the high-power-frequency-band PRB which is required by normal running of a system, the dynamically set high-power-frequency-band PRB of the current cell, the static high-power-frequency-band PRB which is distributed to the current cell in advance, and the load balancing degree of the edge user of the current cell and the edge user of the adjacent cell. By the method and the device, the downlink interference can be reduced, the adjusting frequency of the high-power-frequency-band PRB can be reduced and the stability of an LTE system can be improved.

The invention relates to a parallel voltage stabilizing circuit which has large output power, low operation power, simple structure and low cost. The parallel voltage stabilizing circuit comprises a voltage detection and control unit M1, a regulating tube Q1 and an isolated diode D1; wherein the output voltage end VIN is connected with the anode of the isolated diode D1 and the current input end of the regulating tube Q1, the cathode of the isolated diode D1 is connected with the power input end of the voltage detection and control unit M1, and the power output end of the voltage detection and control unit M1 is connected with the output voltage end VDD; the control output end of the voltage detection and control unit M1 is connected with the control end of the regulating tube Q1; the current output end of the regulating tube Q1 is connected with a system ground GND; and the regulating tube Q1 is correspondingly controlled to switch on or off when the voltage detection and control unit M1 detects that the voltage at the output voltage end VDD is higher or lower than a preset value so as to ensure that the output voltage end VDD is stabilized.

The invention provides a heartbeat information regulation method and a heartbeat information regulation system for a network system. The method comprises the following steps of: fuzzifying an accurate value to obtain a fuzzified heartbeat interval value in a current regulation period in the process of acquiring heartbeat interval information in the current regulation period; and if the fuzzified heartbeat interval value in the current regulation period is different from that in the previous regulation period, regulating a heartbeat interval used by the system.

The invention provides a ship navigation control online self-adaptive adjustment method, which comprises the following steps: S1, setting an ideal ship route, if no wind wave flow disturbance force dominant direction exists, taking the ship bow direction as the ship navigation control direction, and otherwise, entering the step S2; S2, measuring the magnitude and vector direction of the wind waveflow disturbance force in real time, and setting an output value of a ship main engine and an included angle between the ship heading and an ideal ship route, wherein the vector direction of the resultant force of the propeller thrust and the wind wave flow disturbance force is the direction from the current ship centroid to the nearest reference point; S3, adjusting the included angle between theship heading and the ideal ship route and / or the output value of the ship main engine, and achieving interaction of the vector direction of the resultant force with the ideal ship route, wherein theincluded angle is smaller than a set threshold value; and S4, adaptively controlling a ship steering engine according to the acquired course deviation value, keeping the ship deviated from the coursewithin an allowable range, and repeating the steps S3 and S4. The invention further provides a ship navigation control online self-adaptive adjustment system.

An iron and steel enterprise oxygen scheduling optimization system and an iron and steel enterprise oxygen scheduling optimization method belong to the technical field of iron and steel enterprise informatization. The iron and steel enterprise oxygen scheduling optimization system comprises the components of an equipment working condition type definition module, a working condition oxygen characteristic management module, a working condition combined tool module, an optimal solution settling module, a scheduling plan storing and playback module, etc. The equipment working condition type definition module, the working condition oxygen characteristic management module, the working condition combined tool module, the optimal solution settling module and the scheduling plan storing and playback module are operated on a scheduling computer. The working condition type data, the working condition oxygen characteristic data and the scheduling solution data are stored in relationship database software. The relationship database software is operated on a server. The scheduling server is connected with a server through a local area network. The iron and steel enterprise oxygen scheduling optimization system and the iron and steel enterprise oxygen scheduling optimization method have advantages of settling an oxygen fine scheduling problem, providing an easy-interaction oxygen scheduling system, helping oxygen scheduling personnel improve scheduling level and reaction speed, reducing oxygen cost, reducing scheduling frequency of oxygen generating equipment and improving production stability.

The invention discloses an IGBT (insulated gate bipolar transistor) carrier frequency control method and is applied to control of the IGBT carrier frequency of a motor controller of an electric vehicle. The method comprises steps of monitoring a motor current value under the condition that an electric vehicle is started; determining a first switching frequency of the IGBT according to the motor current value and a first preset corresponding relation, wherein the first preset corresponding relationship is an optimal solution of the corresponding relationship between a motor current value and the IGBT switching frequency obtained by the IGBT for control efficiency of the motor controller in the specified working noise environment; and adjusting the carrier frequency of the IGBT to the firstswitching frequency. The invention further discloses a control device of the IGBT carrier frequency and an electric automobile.

The invention discloses a wheel type diamond knife scribing method. The method includes the main steps that firstly, a wafer is thinned to a target thickness, and the back technology is completed; secondly, the wafer is fixed to a tensioning ring through an adhesive membrane; thirdly, a wheel type diamond knife is used for scribing of the water after the step, the pressure and the speed are set, and a groove is formed; fourthly, the wafer is subjected to splintering along the groove by means of a splintering machine; fifthly, the wafer is divided to form independent chips. The process has the advantages that diamond knife scribing is adjusted from traditional pen type scribing to wheel type scribing, and the problems that when a traditional diamond knife is used for scribing high-hardness semiconductor materials like SiC and GaN, the knife is large in loss, high in cost and low in efficiency can be well solved. Compared with adhesive wheel scribing and laser scribing, the diamond knife has larger advantages in the aspect of high-hardness semiconductor material scribing, and is wide in market application prospect.

The invention relates to the technical field of automatic voltage control in an electric system, in particular to a relaxation reactive voltage optimizing system based on province-district coordination and a working method of the relaxation reactive voltage optimizing system. At the present stage, local areas are administered by a dispatcher control center, the voltage regulation capacity can not be used sufficiently, and even voltage quality is affected because the regulation effects among the areas are opposite. The relaxation reactive voltage optimizing system comprises an obtaining module, a calculating module, a sending module, a processing module and a receiving module, wherein the obtaining module is used for obtaining a power grid model and real-time data; the calculating module is used for performing state estimation on collected data and performing relaxation voltage reactive power optimization calculation to obtain a coordination strategy; the sending module is used for sending the coordination strategy to a district dispatcher; according to the processing module, the coordination strategy is received by the district dispatcher and then processed to control actions, and if a province dispatcher is needed for matching, the upper and lower bounds of expected voltage are reported; according to the receiving module, a voltage coordinating request of the district dispatcher is received by the province dispatcher and serves as the optimization constraint of next circulation. According to the technical scheme, on the premise of ensuring qualified voltage, regulating frequency of a discrete device is reduced, network loss is effectively reduced, and convergence reliability of an optimization algorithm is improved.

The present invention discloses a method for tuning active control parameters based on a second level power disturbance of a photovoltaic power station. The photovoltaic power station is connected toa power grid. The method comprises the following steps: characteristic parameters of the power grid are obtained; and the characteristic parameters include a frequency fluctuation characteristic parameter of the power grid, a primary frequency modulation characteristic parameter of a traditional generator set and a set frequency of the power grid. A frequency modulation dead zone target value, a frequency modulation limiter and a droop characteristic parameter in the active control parameters of the photovoltaic power station are determined according to the characteristic parameters so that the frequency modulation of the photovoltaic power station and the primary frequency modulation of the traditional generator set are successively operated in a time dimension and operated stage by stagein a frequency dimension. The invention tunes the active control parameters of the photovoltaic power station according to the actual situation of the photovoltaic power station access to the power grid, is conducive to giving full play to the active control performance of the photovoltaic power station, improves the immunity of the photovoltaic power station to the second level power disturbanceof the power grid, and is conducive to the rapid recovery of the power grid after a large disturbance.

The invention belongs to the technical field of electronic protective film processing, and particularly relates to a feeding device for electronic protective film processing. The feeding device comprises a feeding module and a mounting frame; and two semicircular grooves are symmetrically formed in one side of the top of the mounting frame. According to the feeding device, the angle of a rotatingrod is adjusted through a crank, a round rod sleeved with an electronic protective film winding drum is conveniently adjusted to be located at the top of the mounting frame, the two ends of the roundrod are fixed through semicircular fixing clamps, a driven gear is engaged with a driving gear, and a second motor drives a linkage belt to rotate, so that the round rod rotates, an electronic protective film can be conveniently released, and when the electronic protective film is released, a worker can conveniently take the other electronic protective film winding drum to be connected with one round rod under the round rod in a sleeving manner, continuous feeding of the electronic protective films can be guaranteed, the electronic protective films can be conveniently replaced, the number of workers can be reduced, and the working efficiency can be improved.

The invention discloses a modular industrial control board and belongs to the field of industrial measurement and control systems. The modular industrial control board solves the problems that existing industrial control boards are single in function, can only achieve basic and fixed functions and is insufficient in flexibility. The modular industrial control board comprises an ISA control mother board, an A / D parallel input module, a D / A parallel output module, a D / I parallel input module and a D / O parallel output module are configured on the ISA control mother board, the ISA control mother board comprises a main board CPLD and a bus drive module, the main board CPLD and the four modules are connected on an ISA bus in a hanging mode through the bus drive module, and an address bus and a control bus are connected between the ISA bus and the main board CPLD; chip select signals and read-write control signals of the main board CPLD are output to the four modules; type feedback signals of the four modules are output to the main board CPLD.

The invention discloses a detection device for electrical automation equipment, and the device comprises a bottom plate, a clamping mechanism is disposed above the bottom plate, a placement plate is disposed at the center of the upper surface of the bottom plate, the lower surface of the placement plate is fixedly connected with the upper surface of the bottom plate, and a top plate is disposed above the upper surface of the bottom plate. According to the detection device of the electrical automation equipment, through cooperation of the bottom plate, the clamping mechanism, the placement plate, the top plate, a knob, a sleeve, a first adjustable telescopic rod, a right-angle block, a second adjustable telescopic rod and a detection probe, two sliding blocks can slide inwards in a cavity through transmission of an inclined rod, that is, two clamping plates synchronously move inwards at the same time; and the inner side surfaces of the two clamping plates can be sequentially clamped with the outer side surface of the to-be-detected workpiece, and the to-be-detected workpiece can be located at a relatively central position of the upper surface of the placement plate in the clamping process, so that efficient operation of detection personnel is facilitated.

The invention discloses a method for constructing a bridge deepwater foundation steel pile casing, which relates to a construction scheme of a floating transportation and boat type floating platform positioning system and an air pressure raising and reducing method of the bridge deepwater foundation steel pile casing. The method comprises the following two steps of: after transporting the steel pile casing to a pier position by floating, performing precise planar positioning on the steel pile casing by an adjusted boat type floating platform positioning system; and inflating the steel pile casing by an air compressor to jack the steel pile casing. In the method, a formed steel pile casing is transported in position by floating, the steel pile casing is submerged by the air pressure raising and reducing method, and the self-weight of the steel pile casing and an anchorage system of the floating platform ensure that the verticality of the steel pile casing and a central plane position of the steel pile casing and a pile foundation can meet the precision required by design and construction. The construction method of the invention is suitable for the construction of deepwater pile foundation engineering under the conditions that river beds are inclined uncovered rocks and the like on which fixed drilling platforms cannot root, or lakes, reservoirs (comprising tidal rivers) and the like have the water depth of less than 60 meters and the common wind power of lower than 5 grade.

The invention discloses a precision tubular microporous aerator mounting and detecting system and a precision tubular microporous aerator mounting and detecting method. The precision tubular microporous aerator mounting and detecting system consists of a workbench, a mounting facility and a detecting facility, wherein the mounting facility and the detecting facility are arranged on the workbench; through a mounting pneumatic switch and a detection switch, mounting and detection of tubular microporous aerators are switched; through an air compressor or an air blower, an air source is generated; the air source is connected with a pressure reducing valve through a pipeline; a filter is connected to a pneumatic valve; the mounting pneumatic switch is mounted between the filter and the pneumatic valve; the mounting pneumatic switch controls the air source entering the pneumatic valve; the mounting facility and the detecting facility are connected with a main controller; and the main controller collects, stores, sorts and analyzes data information of each tubular microporous aerator. The precision tubular microporous aerator mounting and detecting system is scientific in structure, reliable in performance, easy to manufacture, convenient to use, easy to operate and precision in mounting, and is especially applicable to urban sewage treatment, new construction and expansion of a large factory and reconstruction of an old aeration tank.

The invention relates to the technical field of concrete strength detection, in particular to concrete strength detection equipment for post-disaster house safety identification. The concrete strengthdetection equipment comprises a bottom plate, wherein universal wheels are arranged on the bottom plate, the bottom plate is provided with a stable structure, a lifting structure and a brake structure, the lifting structure comprises a first driving motor, an n-shaped frame, a fixed pulley, a sliding plate and a steel rope, the first driving motor is provided with a winding roller connected withthe steel rope, the n-shaped frame is provided with the fixed pulley, the steel rope is provided with the sliding plate, the sliding plate is provided with a rotating structure, the rotating structurecomprises a third driving motor and a second L-shaped supporting plate, the second L-shaped supporting plate is connected with the sliding plate, the second L-shaped supporting plate is provided withthe third driving motor, the third driving motor is provided with a rotating rod, the rotating rod is provided with a connecting circular plate, the connecting circular plate is provided with a firstL-shaped supporting plate, the first L-shaped supporting plate is provided with an adjusting structure, the adjusting structure is connected with an electric push rod and a supporting plate, and theelectric push rod is provided with a resiliometer. According to the concrete strength detection equipment, the height adjusting range of the resiliometer is wider, and the resiliometer is convenient to use when positions with different heights are detected.

The invention discloses a medium-concentration pulping feeding device with stable pulping intensity and a feeding method thereof. The medium-concentration pulping feeding device comprises a flow rate control system, a pulp inlet pipe, a buffer pipe and an overflow pipe, wherein the feeding end of the buffer pipe is connected with a discharging opening of a medium-concentration pulp pump through the pulp inlet pipe, the discharging end of the buffer pipe is connected with a feeding opening of a medium-concentration disc grinding machine, the feeding end of the buffer pipe is an expansion opening with the inner diameter changed from the small size to great size, the discharging end of the buffer pipe is a contraction opening with the inner diameter changed from the great size to small size, an included angle between the skew wall of the expansion opening of the feeding end and a center shaft of the buffer pipe is 15 degrees to 45 degrees, and an included angle between the skew wall of the contraction opening of the discharging end and the center shaft of the buffer pipe is 15 degrees to 45 degrees. According to the method, the pulping intensity is calculated in real time through the flow rate control system according to the work power of the medium-concentration disc grinding machine and the real-time detected paper pulp flow rate passing through the disc grinding machine, and the ratio value of the real-time pulping intensity to the set pulping intensity is controlled to be 95 to 105 percent. The medium-concentration pulping feeding device and the feeding method have the advantages that the disc grinding machine is enabled to carry out pulping at stable pulping intensity, and the stable pulping effect is obtained.

The invention discloses a paper cutter bed guide mechanism. The guide mechanism comprises a main rack and a secondary rack, wherein a bed is arranged between the main rack and the secondary rack, the two reverse surfaces of the cutter are respectively in slide fit with the opposite surfaces of the main rack and the secondary rack; the main rack is provided with a pair of pilot holes, and eccentric bushings are respectively arranged in the pilot holes and are locked and fixed in the pilot holes of the main rack by nuts; a connecting shaft is arranged in the eccentric bushing and is in clearance fit with the eccentric bushing; the bed is provided with a pair of chutes corresponding to the connecting shaft; a liner guide rail pair is arranged in the chutes; the slide block of the liner guide rail pair is fixed on the connecting shaft; a transition connecting block is fixed on the side surfaces of the chutes; and the guide rail of the liner guide rail pair is fixed on the transition connecting block. The invention has the characteristics of favorable wear-resisting performance, long service life, high operation precision, low noise, compact and simple structure, high processing efficiency, time and labor saving, low manufacturing and maintaining cost and the like.

The invention discloses a coal preparation plant main coal washing production method, and relates to the technical field of coal mines. The method comprises the following steps that S1, equipment is checked, and specifically equipment parameters and technological parameters are checked before starting; S2, equipment of a main coal washing system is made to form a closed relation; S3, one-key centralized control starting is carried out on the main coal washing system; S4, used materials of the main coal washing system are controlled; and S5, collected information is transmitted to a mobile terminal through an information management system. The method has the advantages that the on-site production safety and the production efficiency are improved, the fault shutdown probability is reduced, apart of unsafe factors generated after equipment heavy load shutdown are avoided, the starting time is shortened, the starting interruption is avoided, and the economic effect is greatly improved.

The invention provides a refrigerator control method and a computer storage medium. The refrigerator control method includes the steps of: detecting the environment temperature of the environment where the refrigerator is located; when the environment temperature is larger than or equal to a first preset value and smaller than a second preset value, controlling a draught fan for enabling operationat a first rotating speed for a first preset duration; acquiring a first average value of the environment temperature within the first preset duration; judging whether the first average value is smaller than the first preset value; and if so, controlling the draught fan for enabling operation at a second rotating speed for the first preset duration, wherein the first rotating speed is larger thanthe second rotating speed. According to the scheme of the invention, when the first average value of the environment temperature within the first preset duration is smaller than the first preset value, the fan is adjusted from the first rotating speed to the second rotating speed rather than immediate adjustment when the environment temperature is smaller than the first preset value, a delay timeis increased when the rotating speed of the fan is adjusted, thus lowering the adjusting frequency of the rotating speed of the fan, avoiding too frequent adjustment of the rotating speed of the fan,and effectively prolonging the service life of the fan.

The invention relates to the field of home decoration equipment, in particular to an indoor decoration device. The indoor decoration device solves the problems that a painting device is low in automation degree and working efficiency in indoor decoration in the prior art. The indoor decoration device comprises a fixing block for a painting mechanism, wherein the fixing block is arranged on a screwrod type lifting frame; the painting mechanism is arranged on the fixing block; a displacement line is parallel to the horizontal plane; a horizontal motor is arranged at one end of a screw rod; a horizontal sliding block is arranged on the screw rod and is connected with the painting mechanism; a pressure adjusting device is arranged between a painting roller of the painting mechanism and the horizontal sliding block in order to enable the painting mechanism to be attached to a treated wall tightly; and an automatic feeding mechanism is arranged at one side, away from the horizontal motor, of the fixing block. The indoor decoration device has the advantages that the position of the painting roller can be adjusted, and the adjusting frequency in working is reduced; and excessive feeding is avoided, the pressure between the painting roller and the wall is fixed, and the uniform painting is achieved.