FI75551C - STYRSYSTEM FOER LYFTKRAN. - Google Patents

Description

1 75551

Crane control system

The dynamic loads must be taken into account in the strength design of the crane structure. They are synthesized both by the accelerations and decelerations of the boom itself and especially of the load to be lifted.

The maximum permissible speed of the crane boom is determined by a hydraulic pump, the volume flow of which is set to a certain maximum level for each crane. The available volume flow is divided into different actuators, mainly hydraulic cylinders, by control valves which are mechanically controlled by means of levers.

A serious drawback has been that the maximum permissible load and speed of the crane have been fixed and independent of each other, ie the crane has had to be dimensioned on the basis of its frequent practice of shifting the maximum load at maximum speed. It has been possible to start and stop the boom very quickly, as a result of which the crane structure is often subjected to vibration during load transfer. Attempts by the pilot to repair it have usually only aggravated the vibration, because the steering movements and the natural frequency of the crane structure together have formed an unattenuated vibration movement.

This has been because the movements of the crane actuators, mainly the valves of the hydraulic cylinders, have been controlled directly mechanically. According to the perception in the industry, the magnitude of the accelerations could not be much influenced by reducing the opening and closing speeds of the control valves, because then the control of the crane would require 30 predictions and would become inaccurate, even dangerous.

U.S. Pat. No. 4,006,347 proposes that the load be taken into account by slowing down the movement of the crane boom in the vertical plane as the boom pivots from the top to the horizontal position, and correspondingly accelerating as the boom moves from 1 to 35 degrees upwards. However, the control is indirect by means of an additional 2 75551 valve which directs part of the volume flow produced by the hydraulic pump past the hydraulic cylinder valve back to the tank, which is why the control is inaccurate, especially during the boom start and stop phases.

The invention thus relates to a system for controlling a boom of a hydraulic crane in particular, wherein the crane is provided with at least one load cell, the measurement data of which adjusts the boom speed so that the maximum permissible speed increases as the load decreases and decreases as the load increases.

The aim is to provide a new steering system which takes better account of the dynamic loads on the crane than known systems.

The system according to the invention is mainly characterized in that, in order to reduce the dynamic stresses on the crane, the flow of hydraulic actuators is controlled by directly controlling the movements of the actuator valves on the basis of the boom speed reference value.

In the control system according to the invention, the dynamic stresses caused by the acceleration of the load are thus reduced by preventing the control valve from opening and closing too quickly and by reducing the speeds of the crane, especially at high loads. Filtering user control movements reduces accelerations, dampens the detrimental effects of error movements, and improves control characteristics. Reduced dynamic tension oscillation bones can increase the crane's lifting capacity, improve steering characteristics, increase the durability of boom structures or lighten structures.

The hydraulic valves are electrically controlled. The driver-controllable oil flow is regulated by limiting the above-mentioned electronic control message on the basis of 35 load information.

3 75551 In this case, the oil volume flow is controlled by the same valve that controls the crane. The advantage of this order is that there is no need to increase the number of hydraulic components from the current one.

5 It is advantageous to construct the crane speed control system, for example, as follows.

The system includes a programmable digital control unit that performs maximum speed control based on information from the load cell. The control unit 10 also includes a digital filter section that monitors the speeds of movement of the joysticks and filters out excessive frequencies, as well as performs accelerations and decelerations on the embankment. All control and monitoring features of the control unit can be programmed for each crane and actuator.

The invention will now be described in more detail with reference to the accompanying drawing.

Figure 1 shows a side view of the crane.

Figure 2 shows a schematic diagram of the control system.

Figure 3 shows a block diagram of an electronic control unit.

Figure 4 shows a block diagram of a preferred example program placed in the program memory included in the control unit.

Figure 5 shows the function of pressure and velocity in Example-25.

The exemplary crane according to Figure 1 comprises a base 1, a column 2, a lifting boom 3, a transfer boom 4 and this extension 5 / grab 6, a lifting cylinder 7 and a transfer cylinder 8.

The load on the crane places the greatest load on the column 2 and the lifting cylinder 30, as a result of which the preferred location of the at least one load cell included in the system is in connection with either the column or the lifting cylinder. For example, the load cell may measure the pressure in the lifting cylinder, or in its supply hose, or a stress measuring sensor may be attached to the surface of the column.

4 75551

Suitable sensors are readily available, so it may not be necessary to explain their structure and operation in more detail here.

In Fig. 2, block 9 shows the electronic control unit, block 10 the control valve system and block 11 the controllable actuators (hydraulic cylinders). Arrow 12 indicates the power supply line, arrow 13 user speed instructions, arrow 14 load information, arrow 15 valve control signal, and arrows 16 and 17 Ö1 grain flow.

In Fig. 3, reference numeral 18 denotes a load sensor from which the voltage message 19 is converted in digital form in the analog-to-digital converter 20 to the microprocessor 21. The speed instructions 23 obtained from the control potentiometers 22 are also converted in digital form in the A / D converter 20 to the above-mentioned micro-15 processor 21. Based on the speed instructions and the load message, the microprocessor 21 performs the speed instruction adjustment and filtering calculation according to the control software located in the non-volatile memory 24. The modified speed instructions 25 are sent to the control valves 26 sar -'- · 20 and from the traffic controller 27. The control variable of the valve can also be an analog electrical message, in which case a digital / analog converter and a suitable amplifier are used instead of the serial controller.

A preferred embodiment is explained in more detail below.

25 The system consists of a digitally controlled control valve, control electronics, electronic control levers and a pressure sensor.

There are 2 control levers attached to the driver's seat, each of which can control three actuators (hydraulic cylinders), either simultaneously or separately. Three potentiometers are placed on the control lever so that when the lever is turned horizontally, two potentiometers are deflected from their center position to one or the other, and when the pushbuttons placed on the lever are pressed, the third potentiometer is deflected. All potentiometers are connected in parallel to 5 75551 nan 5 V DC, so when the potentiometer slides in the middle position, the output voltage is 2.5 V. Thus, a total of 6 output voltages are obtained from the control lever, which vary between 0 V and 5 V. depending on the current position of the trees. When the output voltage is <2.5 V, the hydraulic cylinder moves in and correspondingly, when the voltage is> 2.5 V, the hydraulic cylinder moves out, ie its length increases. When the voltage is 2.5 V, the cylinder is in place. The closer each output-10 voltage is to 0 V or 5 V, the higher the speed reference. the actuator receives.

Em. the control voltages are connected to a control unit where data is edited and processed and forwarded to the control valves. The control unit contains e.g. 15 microprocessors, ie processor, analog-to-digital converter, program memory, working memory, serial communication controller and oscillator crystal. The program memory is of the read-only memory type, which is programmed by a separate programming device. Program memory data is retained over electric cat-20 revenge. A control program is in the form of an infinite program loop that is executed several times per second while the device is operating. The block diagram of the program placed in the program memory is shown in Figure 4. When the voltage is connected to the control unit, the processor starts to execute the program in the program memory. Initially, the interrupt controller and the initializations required by the serial communication controller are performed by writing certain bytes in the registers of the above controllers (30).

Execution of the actual program loop begins with reading control messages. These control messages are the control voltages from the above-mentioned controller-30 rods (6 pcs.) And the voltage from the pressure sensor. A strain gauge type sensor with a maximum output of 100 mV at a supply voltage of 10 V at 75551 o is used as the pressure sensor, so the pressure message is amplified to 0 - 5 V before the analog / digital converter. The analog / digital converter converts the voltages corresponding to the control messages into digital form (0 -255 in decimal) (31). After this, the pressure message is filtered so as to find out the average pressure level in the lifting cylinder, which does not show the pressure peaks caused by the load fluctuations. Filtering prevents the control system from resonating with load fluctuations (32). A mathematical algorithm is used for filtering, where the new filtered value is obtained by adding to the previous filtered value the difference between the reference value and the previous filtered value, multiplied by a certain parameter, ie X2 = Xl + a * (O - Xl), where Xl = previous filtered value, X2 = new filtered 15 value, a = parameter, O = setpoint. Changing parameter a provides the desired filtering function. In practice, the filtering causes the new filtered value X2 to reach the setpoint O embanked, i.e. at a certain filter-specific rise time.

20 Next, the control messages received from the joysticks are also filtered using the above algorithm (33). The filtering parameters of the various control messages can be selected to suit each crane. Filtering the control messages reduces the opening and closing speeds of the desired control valves and thus the accelerations and decelerations of the actuators and the load.

The speed adjustment of the individual actuator is performed on the basis of the pressure message (34). The control program increases the maximum permissible speed of the actuator as the pressure message decreases and correspondingly decreases as the pressure message increases, for example according to the graph of the function in Fig. 5. The effect of the pressure message on the maximum actuator speed may vary from actuator to actuator.

The control messages initially measured from the joysticks have been modified to be sent to the steering valves based on the control and load status of the nos-35 Tur. At the end of the program loop, control messages are sent via the serial communication controller to the valves (35). The control valve used is a valve that can be controlled by serial digital control.

5 The valve itself handles the interpretation of the control signals and adjusting the valve to the desired position.

The crane generally has several control valves for different movements, which valves are outlined in Fig. 3 for simplicity only with dots 28. As shown in Fig. 10, the operation of all necessary valves can be changed, as desired by actuator and crane, by changing the control software.

Claims (4)

8 75551 A system for controlling, in particular, a hydraulic crane boom, the crane being provided with at least one load cell, the measurement data of which adjusts the boom speed so that the maximum permissible boom speed increases as the load decreases and correspondingly decreases as the load increases. that in order to reduce the dynamic stresses on the crane, the grain flow of the hydraulic actuators is controlled by directly controlling the actuations of the actuator valves based on the boom speed reference (13) and the load message (14) and filtering out boom speed instructions according to which the valve travel A system according to claim 1, characterized in that the hydraulic valves are electrically controlled and in that the driver-controllable oil flow is regulated by limiting the electrical control message on the basis of the load information. A system according to claim 2, characterized in that the volume flow of oil is controlled by the same valve with which the crane is otherwise controlled. A system according to claim 1, characterized in that it comprises a programmable, preferably digital control unit for controlling the maximum speed, which control unit preferably also includes a digital filter part for monitoring the movement speeds of the joysticks and filtering out excessive frequencies.