The invention provides a division for an invention with the application date of 2016, 11, 22, the application number of CN201611039763.2 and the name of 'a robot hydraulic drive rotary joint closed-loop control system'.
Background
The rotary joint is one of the joints which are most widely applied in the field of industrial robots at present. Generally, a motor is adopted to directly drive a rotary joint, and the number of the rotary joints driven by hydraulic pressure is small. Because hydraulic transmission has the problems of leakage, compressible transmission fluid and the like, the movement of the hydraulic transmission is difficult to accurately control. Further, when the load changes, an impact is easily generated. The traditional method mostly adopts an electromagnetic proportional control valve to control the flow, but the electromagnetic proportional control valve is expensive, and most high-end products are monopolized by foreign countries, so that the control cost is higher. Therefore, a control system and a method thereof with low control cost, precise position control and good motion stability are needed.
The invention discloses a closed-loop force control system and a control method based on a hydraulic control mode, wherein a force closed-loop control parameter is acquired according to a controller module and a voice signal is executed, the output stepping amount of a hydraulic cylinder is set according to the control parameter, whether output force control is carried out or not is judged, if yes, a DSP module samples the pulling force detected by a feedback measuring element, the pulling force is used as a force feedback value of a force closed-loop control algorithm, the DSP module carries out increment PI calculation according to the force closed-loop control parameter acquired by the voice module and the force feedback value, and the calculated value is used as an input value of a hydraulic control element. The closed loop force control system and the control method provided by the invention can provide safe and reliable pulling force for a patient in a forearm fracture operation, but the invention has poor motion stability in force output control.
Patent application No. 201410119355.2 discloses a robot revolute joint driving device, which comprises a driving mechanism and an execution output mechanism; the driving mechanism comprises a servo motor and a hydraulic pump, the execution output mechanism comprises two groups of hydraulic cylinders which are arranged in parallel, a swing rod is connected between pistons of the two groups of hydraulic cylinders, and the swing rod can swing by the rotation center of the swing rod under the driving of the pistons at the two ends; the robot part is connected to the rotation center of the swing rod and rotates along with the swing of the swing rod; the driving device further comprises a detection module, a processing module and a motor controller. The hydraulic actuating mechanism is driven to output by the servo motor, so that the output power is high, and the requirement that the rotary motion robot needs a high-power and compact-structure rotary joint can be effectively met. The intermittent unidirectional circulation motion of the transmission shaft is realized by adopting unidirectional bearing transmission. The rotation amount of the robot part is effectively adjusted by adopting the matching action of the transmitter and the amplifier, but the invention has poor motion stability in force output control.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention provides a robot hydraulic drive rotary joint closed-loop control system, which comprises a drive mechanism, an execution mechanism and a control mechanism, wherein a power module supplies power for the system, and is characterized in that: the driving mechanism comprises a direct current motor, the direct current motor is connected with a gear pump, the executing mechanism comprises a hydraulic rotating joint, the control mechanism comprises an upper computer, the control system further comprises a motor driver, a signal acquisition card and a three-position four-way electromagnetic directional valve, the upper computer is connected with a lower computer through a USB interface, the gear pump is connected with the three-position four-way electromagnetic directional valve, an oil path of the three-position four-way electromagnetic directional valve is connected with the hydraulic rotating joint, pressure transmitters are arranged on an oil inlet pipeline and an oil outlet pipeline of the three-position four-way electromagnetic directional valve, the pressure transmitters are connected with the signal acquisition card, a potential sensor is arranged on the hydraulic rotating joint and connected with the signal acquisition card, the signal acquisition card is further connected with the upper computer, and the upper computer;
the motor is connected with the gear pump through a coupler, an output oil path of the gear pump is connected with the three-position four-way electromagnetic directional valve, the pressure transmitter is connected to an oil inlet pipeline and an oil outlet pipeline of the electromagnetic directional valve, and is respectively an oil inlet pressure transmitter and an oil outlet pressure transmitter and used for measuring pressure values of an oil inlet pipeline and an oil outlet pipeline of a hydraulic system, converting the pressure values of oil in the pipelines into analog electric signals and sending the analog electric signals to the signal acquisition card; the oil inlet pressure transmitter and the oil inlet overflow valve are both connected to the oil inlet pipeline, and the oil inlet overflow valve provides overload protection for the oil inlet pipeline; the oil outlet pressure transmitter and the oil outlet overflow valve are both connected to the oil outlet pipeline, and the oil outlet overflow valve provides certain back pressure for the oil outlet pipeline;
after the upper computer receives the pressure values of the oil inlet and the oil outlet, calculating a pressure difference delta P which is Pi-Po, wherein Pi is the pressure value of the oil inlet, and Po is the pressure value of the oil outlet; judging whether the load changes or not according to the pressure difference delta P, adjusting the value of the duty ratio D of PWM (pulse-width modulation) for controlling the rotating speed of the motor in real time according to the change of the load, sending the value of the duty ratio D to a motor driver by an upper computer through a CAN (controller area network) bus communication module, and controlling the rotating speed of the direct current motor by the motor driver according to the obtained PWM value; the relation between the duty ratio D and the pressure difference delta P in the PWM is as follows: d ═ κ Δ P, κ is a proportionality coefficient;
the upper computer calculates a difference value between the pressure value of the oil inlet and the pressure value of the oil outlet detected by the pressure transmitter, when the pressure difference is increased, the load is increased, the PWM duty ratio D is increased by the upper computer, and the motor is accelerated to adapt to the increase of the load; when the pressure difference is reduced, the load is reduced, the upper computer reduces the PWM duty ratio D, the motor reduces the speed to adapt to the reduction of the load, the upper computer compares the current position of the hydraulic rotating joint detected by the potential sensor with the target position in real time, and when the current position of the hydraulic rotating joint detected by the potential sensor is consistent with the target position, the upper computer controls the electromagnetic reversing valve to be switched to the neutral position function, so that the position is locked.
Furthermore, the signal acquisition card is connected with the upper computer through an RS 232-USB module, one end of the RS 232-USB module is connected with the signal acquisition card, the other end of the RS 232-USB module is connected with a USB interface of the upper computer, and the signal acquisition card transmits the pressure value transmitted by the pressure transmitter and the potential sensor and the position of the hydraulic rotating joint to the upper computer.
Furthermore, the pressure transmitter is connected to an oil inlet pipeline and an oil outlet pipeline of the electromagnetic directional valve, is respectively an oil inlet pressure transmitter and an oil outlet pressure transmitter, and is used for measuring pressure values of an oil inlet pipeline and an oil outlet pipeline of the hydraulic system, respectively converting the pressure value of oil in the pipeline into an analog electric signal and sending the analog electric signal to the signal acquisition card.
Furthermore, the electromagnetic directional valve is used for switching to a middle-position function after the hydraulic rotary joint reaches a target position, locking of the oil inlet and the oil outlet is achieved, locking of the position is guaranteed, and when the hydraulic rotary joint needs to change the rotating direction, the electromagnetic directional valve changes the oil inlet and the oil outlet of the hydraulic rotary joint through movement of the valve position.
Furthermore, the potential sensor is used for detecting the position of the hydraulic rotary joint and sending the position to the signal acquisition card.
Advantageous effects
The invention provides a closed-loop control system and a closed-loop control method for a hydraulic drive rotary joint of a robot.
Detailed Description
For a better understanding of the technical solutions and advantages of the present invention, the following detailed description of the present invention is provided in conjunction with the accompanying drawings. In addition, the direct current motor and the motor described in the specification of the present invention are the same concept, the direct current motor driver and the motor driver are the same concept, and the three-position four-way electromagnetic directional valve and the electromagnetic directional valve are the same concept.
Example 1.1
As shown in fig. 1, the robot hydraulic drive rotary joint closed-loop control system provided by the invention comprises a drive mechanism, an execution mechanism and a control mechanism, wherein the drive mechanism comprises a direct current motor 5 and a gear pump 6, the direct current motor 5 is connected with the gear pump 6, the execution mechanism comprises a hydraulic rotary joint 12, the control mechanism comprises an upper computer 1, the upper computer 1 calculates a difference value between an oil inlet pressure value and an oil outlet pressure value detected by a pressure transmitter, when the pressure difference is increased, the load is increased, the upper computer increases a PWM duty ratio D, and the motor is accelerated to adapt to the increase of the load; when the pressure difference is reduced, the load is reduced, the upper computer reduces the PWM duty ratio D, the motor reduces the speed to adapt to the reduction of the load, the upper computer compares the current position of the hydraulic rotating joint detected by the potential sensor with the target position in real time, and when the current position of the hydraulic rotating joint detected by the potential sensor is consistent with the target position, the upper computer controls the electromagnetic reversing valve to be switched to the neutral position function, so that the position is locked.
The system also comprises a lower computer 2, a CAN bus communication module 3, a motor driver 4, a signal acquisition card 7, a potential sensor 10, a three-position four-way electromagnetic directional valve 11, an oil inlet overflow valve and an oil outlet overflow valve 14.
The pressure transmitter comprises an oil inlet pressure transmitter 8 and an oil outlet pressure transmitter 9, the oil inlet pressure transmitter 8 is connected to the oil inlet pipeline, the oil outlet pressure transmitter 9 is connected to the oil outlet pipeline, and the pressure values of the oil inlet pipeline and the oil outlet pipeline are measured respectively; the oil inlet pressure transmitter 8 and the oil outlet pressure transmitter 9 are connected to the signal acquisition card 7, convert the pressure value of the pipeline oil into an analog electrical signal (current value) and send the analog electrical signal to the signal acquisition card 7.
The electric potential sensor 10 is connected to the hydraulic rotary joint 12, and is used for measuring the current rotation angle of the hydraulic rotary joint and converting the angular displacement of the hydraulic rotary joint into a corresponding voltage signal.
The signal acquisition card 7 is connected to the upper computer 1 and used for acquiring signals measured by the oil inlet pressure transmitter 8, the oil outlet pressure transmitter 9 and the potential sensor 10 and sending the signals to the upper computer 1.
The control method is as shown in fig. 2, the upper computer 1 obtains pressure value signals of an oil inlet pipeline and an oil outlet pipeline and position signals of the hydraulic rotary joint 12 through a signal acquisition card 7, calculates a pressure difference value delta P according to the pressure value signals of the oil inlet pipeline and the oil outlet pipeline, judges whether a load changes according to the pressure difference delta P, and adjusts the value of the duty ratio D of PWM for controlling the rotating speed of the motor 9 in real time according to the change of the load; the upper computer 1 sends the value of the duty ratio D to the motor driver 4 through the CAN bus communication module 3, and the motor driver controls the rotating speed of the direct current motor 5 according to the obtained PWM value.
The direct current motor 5 is connected with the gear pump 6, and an output flow model of the gear pump 6 is established as Q (ml) ═ Q × n × v/60 (each letter in the above formula represents Q: flow, Q: average flow per revolution (ml/revolution) of the gear pump, and is related to the structure of the gear, n: gear pump rotation speed (revolution/minute), and v: volumetric efficiency) by combining performance curves of the gear pump 6. The rotational speed of the dc motor 5 determines the output flow of the gear pump 6. When the load of the hydraulic system is constant, the output flow of the gear pump 6 determines the rotation speed of the hydraulic rotary joint. When the load is changed, the moving speed of the hydraulic rotary joint is influenced, and the influence can be counteracted by correspondingly changing the output flow of the gear pump 6, so that the rotating stability of the hydraulic rotary joint is improved.
Specifically, the relationship between the duty ratio D and the pressure difference Δ P in PWM is simplified as follows: d ═ κ Δ P (κ is a proportionality coefficient), when the pressure difference Δ P increases, which indicates that the load increases, the motor 5 needs to accelerate, the upper computer 1 increases the duty ratio D accordingly and sends it to the motor driver 4, and the motor driver 4 drives the motor 5 to accelerate to adapt to the instantaneous increase of the load; and vice versa.
The upper computer 1 obtains the rotation angle of the hydraulic rotating joint through a signal acquisition card 7. The upper computer 1 judges whether the current rotating angle reaches a target rotating angle in real time, if the current rotating angle reaches a specified position, the upper computer 1 gives a signal to the lower computer 2, and the lower computer 2 controls the on-off of a corresponding electromagnetic relay to enable a valve body of the electromagnetic directional valve 11 to be switched to a middle position function, so that the oil inlet and the oil outlet are locked, at the moment, the hydraulic rotating joint is locked at the current position, and a rotating task is finished. When the next task is started, the upper computer judges the rotation direction of the hydraulic rotary joint according to the task, and correspondingly controls the electromagnetic directional valve 11 according to the rotation direction and the steps.
Specifically, the calculation formula of the pressure difference is that Δ P is Pi-Po (Pi: oil inlet pressure, Po: oil outlet pressure); the signal acquisition card 7 is connected with the upper computer 1 through an RS 232-USB module, one end of the RS 232-USB module is connected with the signal acquisition card 7, and the other end of the RS 232-USB module is connected with a USB interface of the upper computer 1. The RS232 to USB conversion module can realize the conversion between the serial interface of the signal acquisition card 7 and the USB interface of the upper computer 1, so as to realize the communication between the signal acquisition card and the upper computer.
The upper computer 1 is connected with the direct current motor driver 4 through the CAN bus communication module 3, the upper computer 1 is connected with the CAN bus communication module 3 through the USB, and the CAN bus communication module 3 is connected with the motor driver 4.
The upper computer 1 is connected with the lower computer 2 through a USB, the lower computer 2 controls an electromagnetic relay to supply switching value to the electromagnetic relay, and the electromagnetic relay controls the on-off of electromagnets at two ends of the electromagnetic directional valve 11 to realize the reversing of the electromagnetic directional valve 11.
The robot hydraulic drive rotary joint closed-loop control system also comprises a power supply module which respectively provides power supplies necessary for normal operation for an upper computer 1(220V), a lower computer 2(5V), a signal acquisition card 7(5V), a motor driver 4(24V), an electromagnetic directional valve 11(24V) and the like.
The closed-loop control method for the hydraulic drive rotary joint of the robot specifically comprises the following steps:
step 1: starting the direct current motor 4, and rotating the direct current motor 4 according to the default PWM duty ratio D0;
step 2: the upper computer 1 judges the rotation direction of the hydraulic rotary joint according to the current position returned by the potential sensor 10 and the target position to be reached;
and step 3: the upper computer 1 sends a corresponding command to the lower computer 2, controls a valve body of the electromagnetic directional valve 11 to move to a corresponding position, opens an oil inlet and an oil outlet, and starts to rotate a hydraulic rotary joint;
and 4, step 4: the upper computer 1 calculates a pressure difference delta P according to pressure values returned by the oil inlet pressure transmitter and the oil outlet pressure transmitter, and adjusts a PWM duty ratio D according to the rule;
and 5: the direct current motor driver 4 realizes acceleration or deceleration of the direct current motor 5 according to the latest duty ratio D;
step 6: the upper computer 1 judges whether the target position is reached or not in real time according to the position information of the hydraulic rotary joint returned by the potential sensor 10, if so, the step 7 is executed, otherwise, the step 4 is executed;
and 7: the upper computer 1 sends an instruction to the lower computer 2 to control the valve body of the electromagnetic directional valve 11 to move to a middle position, the oil inlet and the oil outlet are locked, the position of the hydraulic rotary joint is locked, and one task is finished;
and 8: the direct current motor 5 keeps rotating, and the overflow valve of the oil inlet overflows to wait for the next task.
It should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.