Method for measuring lifting weight by using single sensor

Abstract

The invention discloses a method for measuring lifting weight by using a single sensor. The method comprises the following steps of: 1) obtaining a function relationship between the rotating speed of a motor and the lifting position of a loading platform; 2) recording the rotation angle values of the force sensor, the acceleration sensor and the motor in real time; (3) two moments when the acceleration sensor displays the same numerical value are found; 4) according to a motor rotation angle function relationship, calculating the height of the loading platform at two moments; 5) calculating the distance between two connecting points of the loading platform and the fork arm at two moments, and 6) calculating the lifting weight M. According to the method, the load weight can be measured through one sensor, and on the premise that the measurement precision is guaranteed, compared with the traditional method that multiple sensors are emphasized, the production cost is greatly saved.

Description

Technical Field

[0001] The present invention relates to a device and method for measuring lifting weight, more specifically, to a device and method for measuring lifting weight of an AGV, and more specifically, to a device and method for measuring lifting weight using a single sensor. Background Art

[0002] AGV is an automatic navigation transport vehicle, which is mainly used in the fields of industry and logistics. It can complete logistics transportation, loading and unloading without human intervention. However, most of the existing AGVs only have the function of transporting goods, and do not have the function of measuring the weight of the loaded goods during the lifting process. To know the quality of the loaded goods, most of the existing AGVs measure the weight of the goods with weighing equipment before transporting the goods, and then transmit the weight data to the car and associate it with other data before moving the goods to the loading platform of the car for subsequent transportation tasks. In actual implementation on site, this method not only increases the process and time of the entire transportation process, but also requires additional cargo weighing equipment to measure the weight in advance. Therefore, although this traditional method can also know the quality of the goods, it is time-consuming and labor-intensive, and seriously affects production efficiency.

[0003] In addition, when the AGV with a scissor-type lifting mechanism has two forks on the left and right, four force sensors are required to be installed between the forks and the load plate. The large number of force sensors greatly complicates installation, inspection, and maintenance. Secondly, although the force sensor can measure the lifting force in real time, due to the impact or lifting acceleration during the lifting process, the measured force is not equivalent to the gravity of the load here, and the dynamic influence needs to be eliminated.

[0004] In view of the above problems, the present invention proposes a device and method for measuring lifting weight using a single sensor. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that the existing AGV trolley cannot be weighed during the lifting process, and to propose a device and method for measuring the lifting weight using a single sensor.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] The method for measuring the lifting weight using a single sensor adopts a real-time weight measuring device for a scissor lift mechanism, including a chassis, a force sensor, an acceleration sensor, a fork arm, a loading platform, a motor, a lead screw, a push block, and a push rod; the fork arm is composed of equal-length straight rods hinged to each other, one end of the bottom of the fork arm is fixedly hinged to the chassis of the AGV trolley, and the other end is movably connected to the chassis of the AGV trolley, one end of the top of the fork arm is fixedly hinged to the loading platform, and the other end is movably connected to the loading platform; the motor is connected to the lead screw, the push block is sleeved on the lead screw, the push block is hinged to one end of the push rod, and the other end of the push rod is hinged to the fork arm; there is one force sensor, which is installed at the hinge between the fork arm and the loading platform; the acceleration sensor is installed on the loading platform.

[0008] The method for measuring the lifting weight using a single sensor specifically includes the following steps:

[0009] 1) Establish a three-dimensional model of the mechanism for simulation. According to the motor control method, the functional relationship H(θ) between the motor speed and the position of the loading platform is obtained by simulation, where H is the height of the loading platform and θ is the encoder angle of the motor;

[0010] 2) Real-time recording of force sensor, acceleration sensor, and motor angle values;

[0011] 3) Find two moments t1 and t2 when the acceleration sensor displays the same value. At t1, the force sensor value is F1, the acceleration sensor value is a, and the motor angle value is θ1; at t2, the force sensor value is F2, the acceleration sensor value is a, and the motor angle value is θ2;

[0012] 4) According to the motor angle function relationship H(θ), calculate the heights H1 and H2 of the loading platform at time t1 and t2;

[0013] 5) Calculate the distances Lt1 and Lt2 between the two connection points of the loading platform and the fork arm at time t1 and t2;

[0014]

[0015]

[0016] Where d is the length of the two equal straight rods that make up the fork arm;

[0017] 6) Calculate the lifting weight M:

[0018] 6.1) If Lt1>Lt2, then the lifting weight M is

[0019]

[0020] 6.2) If Lt1 < Lt2, then the lifting weight M is

[0021]

[0022] The beneficial effects of the present invention are as follows:

[0023] 1. Good economic benefits: This solution realizes the measurement of the load weight through one sensor, greatly saving the production cost compared with the traditional four sensors.

[0024] 2. High safety: When the load quality exceeds the maximum load capacity of the AGV vehicle and when the goods are unevenly loaded, it can be reflected in time to realize the protection function of the equipment.

[0025] 3. In judging whether the AGV vehicle is overloaded, using current judgment can directly reflect the working condition of the servo motor for driving. It can judge whether the motor is overloaded by the magnitude of the current and decide whether to pause the lifting process of the fork arm.

[0026] 4. When using a force sensor to judge whether it is overloaded, by calculating the data read by the sensor, it can effectively reflect the pressure and impact force borne by the upper cover plate. When the sensor reading exceeds the maximum value obtained by calculation, the lifting process of the fork arm is paused. Description of the Drawings

[0027] Figure 1 is the flow chart of the method steps of the present invention.

[0028] Figure 2 is a scissor lift mechanism adopted by the present invention.

[0029] Figure 3 is the force analysis diagram of the load platform at the high lifting position of the present invention. Figure 4 is the force analysis diagram of the load platform at the low lifting position of the present invention.

[0030] In the figure, 1 - chassis, 2 - fork arm, 3 - load platform, 4 - motor, 5 - lead screw, 6 - push block, 7 - push rod Detailed Embodiments

[0031] The present invention will be further described below with reference to the drawings:

[0032] Such as Figures 1 to 3As shown, the method for measuring the lifting weight using a single sensor adopts a real-time weight measuring device for a scissor lift mechanism, including a chassis, a force sensor, an acceleration sensor, a fork arm 2, a loading platform 3, a motor 4, a lead screw 5, a push block 6, and a push rod 7; the fork arm 2 is composed of equal-length straight rods hinged to each other, one end of the bottom of the fork arm 2 is fixedly hinged to the chassis of the AGV trolley, and the other end is movably connected to the chassis of the AGV trolley, one end of the top of the fork arm 2 is fixedly hinged to the loading platform 3, and the other end is movably connected to the loading platform 3; the motor 4 is connected to the lead screw 5, the push block 6 is sleeved on the lead screw 5, the push block 6 is hinged to one end of the push rod 7, and the other end of the push rod 7 is hinged to the fork arm 2; there is one force sensor, which is installed at the hinge between the fork arm 2 and the loading platform 3; the acceleration sensor is installed on the loading platform 3.

[0033] Figure 2 Figure 3 These are force analysis diagrams of the loading platform 3 at two different lifting positions, where F1' and F3' are the support forces of the hinged fulcrums at different heights, and F2' and F4' are the support forces of the sliding fulcrums at different heights. During the lifting process, the weight and the loading platform 3 do not move relative to each other, so there is the following relationship:

[0034] F1'+F2'=G (1)

[0035] G*L2=F1'(L1+L2) (2)

[0036] F3'+F4'=G (3)

[0037] G(L2-Δx)=F3'(L1+L2-Δx) (4)

[0038] The combined formulas yield:

[0039]

[0040] This relationship requires that the acceleration of the fork arm 2 is zero at these two different heights, but it is impossible for there to be a uniform lifting stage in the actual lifting process. Therefore, the moment when the acceleration direction and magnitude of two points in the lifting process are the same is selected for calculation, that is, G in equation (2) and equation (4) should be modified to m(a+g)

[0041] Then we can get

[0042]

[0043] Wherein, L1+L2 and L1+L2-Δx can be converted by the height of the loading platform 3, F1′ and F3′ can be measured by a force sensor, and a can be measured by an acceleration sensor.

[0044] Example 1: Measuring weight during lifting:

[0045] 1) Establish a three-dimensional model of the mechanism for simulation. According to the control method of the motor 4, the functional relationship H(θ) between the speed of the motor 4 and the rising position of the loading platform 3 is obtained by simulation, where H is the height of the loading platform 3 and θ is the encoder angle of the motor 4;

[0046] 2) Real-time recording of the force sensor, acceleration sensor, and the rotation angle value of motor 4;

[0047] 3) Find two moments t1 and t2 when the acceleration sensor displays the same value. At t1, the force sensor value is F1, the acceleration sensor value is a, and the rotation angle value of the motor 4 is θ1; at t2, the force sensor value is F2, the acceleration sensor value is a, and the rotation angle value of the motor 4 is θ2;

[0048] 4) According to the function relationship H(θ) of the motor 4 rotation angle, calculate the heights H1 and H2 of the loading platform 3 at time t1 and t2;

[0049] 5) Calculate the distances Lt1 and Lt2 between the two connection points of the loading platform 3 and the fork arm 2 at time t1 and t2;

[0050]

[0051]

[0052] Where d is the length of the two equal straight rods that make up the fork arm 2;

[0053] 6) Calculate the lifting weight M:

[0054]

[0055] The above embodiments are only preferred embodiments of the present invention and are not limitations of the technical solutions of the present invention. Any technical solution that can be implemented on the basis of the above embodiments without creative work should be deemed to fall within the scope of protection of the patent of the present invention.

Claims

1. A method for measuring lifting weight using a single sensor, characterized in that: It includes the following steps: 1) Establish a 3D model of the mechanism for simulation. According to the control mode of the motor (4), the functional relationship H(θ) between the rotational speed of the motor (4) and the rising position of the load platform (3) is obtained through simulation, where H is the height of the load platform (3) and θ is the encoder angle of the motor (4); 2) Record the values of the force sensor, acceleration sensor, and the rotational angle value of the motor (4) in real time; 3) Find two moments t1 and t2 when the values shown by the acceleration sensor are the same. At moment t1, the value of the force sensor is F1, the value of the acceleration sensor is a, and the rotational angle value of the motor (4) is θ1; at moment t2, the value of the force sensor is F2, the value of the acceleration sensor is a, and the rotational angle value of the motor (4) is θ2; 4) According to the rotational angle function relationship H(θ) of the motor (4), find the heights H1 and H2 of the load platform (3) at moments t1 and t2; 5) Calculate the distances Lt1 and Lt2 between the two connection points of the load platform (3) and the fork arm (2) at moments t1 and t2; where d is the length of the two equal-length straight rods that make up the fork arm (2); 6) Calculate the lifting weight: 6.1) If Lt1 > Lt2, the lifting weight M is 6.2) If Lt1 < Lt2, the lifting weight M is where M is the weight of the lifted object.

2. A real-time weight measuring device for a scissor lift mechanism using the measuring method as claimed in claim 1, characterized in that: It is composed of a chassis (1), a force sensor, an acceleration sensor, a fork arm (2), a load platform (3), a motor (4), a lead screw (5), a push block (6), and a push rod (7); the fork arm (2) is composed of equal-length straight rods that are hinged to each other. One end of the bottom of the fork arm (2) is fixedly hinged to the chassis (1) of the AGV vehicle, and the other end is movably connected to the chassis (1) of the AGV vehicle. One end of the top of the fork arm (2) is fixedly hinged to the load platform (3), and the other end is movably connected to the load platform (3); the motor (4) is connected to the lead screw (5), the push block (6) is sleeved on the lead screw (5), one end of the push block (6) is hinged to one end of the push rod (7), and the other end of the push rod (7) is hinged to the fork arm (2); there is 1 force sensor, which is installed at the hinge joint between the fork arm (2) and the load platform (3); the acceleration sensor is installed on the load platform (3).

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