JPH0255803B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for controlling an articulated robot, and more particularly to a method for controlling an articulated robot that is controlled by a numerical controller and performs automatic processing or assembly. Recently, in various manufacturing departments, efforts are being made to save labor or make products uniform, and the use of robots for machining or assembly has become widespread. FIG. 1 shows a model configuration of an articulated robot with two degrees of freedom, in which a rigid body 10 is rotatably provided with a first arm 12 and a second arm 14 spaced apart from each other by a predetermined distance. Then, the tip end B of the first arm 12
A third arm 16 is rotatably connected to the distal end D of the second arm 14, and a fourth arm 18 is rotatably connected to the distal end D of the second arm 14. A robot hand 20 for working is held. As a result, the connecting mechanism of each arm holding the robot hand 20, that is, the link mechanism forms a robot arm, and by regulating the movement of this robot arm, the position of the robot hand can be controlled. A drive shaft of a first servo motor 22 is connected to the base A of the first arm, and a drive shaft of a second servo motor 24 is connected to the base E of the second arm 14. 2nd servo motor 2
2 and 24, the robot arm is driven to a desired position, and the position and posture of the robot hand 20 are controlled. The first and second servo motors 22 and 24 are rotationally driven by commands from a numerical control device (not shown). In other words, the numerical control device calculates the acceleration characteristics, deceleration characteristics, and maximum speed when moving the robot hand 20 using the arithmetic processing circuit within the numerical control device based on the given parameters, and applies the calculated command speed curve to the calculated command speed curve. A servo motor 22 based on a servo system having a position loop and a velocity loop,
The position of the robot hand 20 is controlled by following the robot hand 24. In this type of conventional method, the command speed curve that controls the position and orientation of the robot hand is created by using a constant inertia of the mechanical system in order to shorten the calculation processing time within the numerical control device and further reduce the capacity of the storage device. Acceleration characteristics, deceleration characteristics, and maximum speed were calculated using only the rotation angle of the motor as a parameter. However, in articulated robots, the load inertia applied to the servo motors 22, 24 varies greatly depending on the posture of the robot arm, and the power of the servo motors 22, 24 cannot be fully exerted when the robot arm is in a posture where the load inertia is small. As a result, the robot hand moves at a slow speed, making it impossible to increase work efficiency. That is, this drawback can be understood from the equation of motion of the five-bar link robot shown in FIG. 1 as follows.
That is, in FIG. 1, the x-axis is a straight line connecting the base of the first arm 12 and the base of the second arm 14,
A perpendicular line is drawn from the midpoint O between the first arm 12 and the second arm ₁₄ , and this is the y-axis. θ ₂ is the inclination between the x-axis and the third arm 16, θ ₃ is the inclination between the x-axis and the fourth arm 18, and θ ₄ is the inclination between the x-axis and the fourth arm 18, and each arm is formed to have the same length. and the third
Midpoints P and Q of arm 16 and fourth arm 18
is the center of gravity of each arm, the coordinates of point P are Px, Py, the coordinates of point Q are q _x , q _y ), and the first
If the torque of the servo motor 22 is _T1 and the torque of the second servo motor 24 is _T2 , then the equation of motion of this five-bar link robot is as shown in equation (1). T _i =J _i θ¨ _i +J ₃ (Dθ ₃ )∂θ ₃ /∂θ _i +J ₄ (Dθ ₄ )
∂θ ₄ /∂θ _i +M ₃ {(Dx _p )∂x _p /∂θ _i + (Dy _p )∂y _p
/∂θi} +M ₄ {(Dx _q )∂x _q /∂θ _i + (Dy _q )∂y _q /∂θ _i
}+Mc{(Dx _c )∂x _c ／∂θi＋(Dy _c )∂y _c ／∂θ _i }...
(1) However, in equation (1), i=1, 2 { D=(θ¨ ₁ ∂/∂θ ₁ +θ¨ ₂ ∂/∂θ ₂ )+(θ〓∂
/∂θ ₁ +θ〓 ₂ ∂/∂θ ₂ ) ² M: Mass of arm J: Moment of inertia of arm. Here, the inertia for the first servo motor 22 is
J _M1 and the inertia with respect to the second servo motor 24 is J _M2 , J _M1 = T _i /θ¨ _i ...(2) However, in equation (2), i = 1, 2. According to the above formula (1), Ti is θ ₁ , θ ₂ , θ〓 ₁ , θ〓 ₂ , θ〓 ₁
, θ¨ ₂ , so from the second equation it follows that J _M1 is a function of θ ₁ , θ ₂ ,
It is a function of θ〓 ₁ , θ〓 ₂ , θ¨ ₁ , θ¨ ₂ . As a result, it can be understood that the magnitude of the load inertia to the servo motors 22 and 24 varies depending on the position, speed, and acceleration of the robot hand. In conventional equipment, the command speed curve is determined by assuming that J _Mi is constant.
The maximum value of J _Mi must be regarded as the virtual load inertia, and therefore, in the posture of the robot arm where J _Mi becomes small, the servo motors 22 and 24 are not able to fully output the power they can produce. Therefore, as mentioned above, there was a drawback that the moving speed of the robot hand decreased. The present invention was made in view of the above-mentioned conventional problems, and its purpose is to be able to fully exert the power of a servo motor regardless of the posture of the robot arm.
An object of the present invention is to provide a control method for an articulated robot that can perform high-speed control of a robot hand. In order to achieve the above object, the present invention provides a method for controlling an articulated robot that controls the posture and position of a working robot hand by driving a servo motor based on a command speed curve that is calculated and generated from desired given parameters. , subdivides the entire working area of the robot hand into multiple areas, and calculates the calculation parameters of the command speed curve for each combination of the area to which the robot hand's starting point belongs and the area to which the end point belongs, taking into account information on the load inertia fluctuation of the servo motor. The present invention is characterized in that the parameters are set in advance, and the position and attitude of the robot hand are controlled at high speed by calculating a speed command curve to be input to a servo system using these parameters. Preferred embodiments of the present invention will be described below based on the drawings and tables. The characteristic feature of the present invention is that the entire working area of the robot hand is subdivided into a plurality of areas, and the calculation parameters of the command speed curve are set for each combination of the area to which the robot hand's starting point belongs and the area to which the end point belongs. The system is configured so that the position and orientation of the robot hand are controlled at high speed by setting the parameters in advance by taking into account information on load inertia fluctuations, and using these parameters to calculate a speed command curve that is input to the servo system. . In this embodiment, the entire work area of the robot hand is divided into three areas A ₁ , A ₂ , and A ₃ as shown in FIG. A command speed curve for the first servo motor 22 and a command speed curve for the second servo motor 24 are respectively calculated by the numerical control device as shown in Table 1 for each combination with the area to which it belongs.

【table】

[Table] That is, in this embodiment, as shown in Table 2, the magnitude of acceleration α, the magnitude of deceleration β, and the magnitude of maximum speed v in the constant speed region are
The calculation results are calculated in advance by taking into account information on load inertia fluctuations No. 2 and 24, and the results of these calculations are stored as calculation parameters in the storage device of the numerical control device. Then, a command speed curve C is calculated in the numerical control device from these predetermined parameters, and the position of the robot hand is controlled based on this result.

【table】

[Table] Therefore, according to this embodiment, the command speed curve can be set to maximize the power of the servo motor according to each posture of the robot arm. Regardless of the situation, the output power of the servo motors 22 and 24 can be fully utilized, and the position of the robot hand can be controlled at high speed. As explained above, according to the present invention, the command speed curve is calculated for each combination of the region to which the starting point of the robot hand belongs and the region to which the end point belongs, taking into account the information on the load inertia fluctuation of the servo motor. As a result of providing the parameters, it is possible to control the posture and position of the robot hand at high speed regardless of the posture of the robot arm. In this example, since the basic shape of the command speed curve is a trapezoidal speed curve, the magnitude of acceleration, the magnitude of deceleration, the magnitude of the maximum speed in the constant speed region, etc. are selected as parameters for determining the command speed curve. However, other parameters may be used as long as they represent the characteristics of the command speed curve. Furthermore, in this embodiment, the work area of the robot hand is divided into three small areas, but if the storage device of the numerical control device has sufficient capacity, it is possible to divide it into even more small areas. By doing so, more effective high-speed control of the position and posture of the robot hand becomes possible. Further, in this embodiment, the working area of the robot hand is shown as a two-dimensional area containing only the position, but this working area can be applied to a multidimensional area including the posture of the robot hand.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a five-bar link showing a model of an articulated robot, and FIG. 2 is a schematic explanatory diagram showing a state in which the entire working area of the robot hand is divided into three parts. In each figure, the same members are given the same reference numerals, 20 is a robot hand, 22 is a first servo motor, and 24 is a second servo motor.

Claims (1)

[Claims] 1. In an articulated robot control method that controls the posture and position of a working robot hand by driving a servo motor based on a command speed curve calculated from given desired parameters, subdivide into areas of
The calculation parameters of the command speed curve are set in advance for each combination of the area to which the robot hand's starting point belongs and the area to which the end point belongs, taking into account information on the load inertia fluctuation of the servo motor, and these parameters are used to calculate the calculation parameters for the servo system. A method for controlling an articulated robot, characterized in that the position and posture of the robot hand are controlled at high speed by calculating a speed command curve as an input.