“When choosing a robot, customers should not only pay attention to the load, but also to the maximum working space at the end of the robot, that is, the reach and the maximum pick-up height of the end of the robot. The arm span refers to the maximum working diameter of the end of the parallel robot on the horizontal plane. The distance from the farthest point of the robot P on the horizontal plane to the center of the robot base is the maximum working radius, that is, half of the arm span. The maximum pick-up height is the maximum vertical movement range, which refers to the range between the lowest point (usually lower than the robot’s moving platform) and the highest point that the robot P can reach.
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When choosing a robot, customers should not only pay attention to the load, but also to the maximum working space at the end of the robot, that is, the reach and the maximum pick-up height of the end of the robot. The arm span refers to the maximum working diameter of the end of the parallel robot on the horizontal plane. The distance from the farthest point of the robot P on the horizontal plane to the center of the robot base is the maximum working radius, that is, half of the arm span. The maximum pick-up height is the maximum vertical movement range, which refers to the range between the lowest point (usually lower than the robot’s moving platform) and the highest point that the robot P can reach.
However, in practical applications, different robots and different application scenarios affect the choice of robot arm span. Especially when selecting robots, the following technical points should be paid special attention to:
1. The reachable working space at the end of the robot is divided into full working space and effective working space
Take a parallel robot as an example. The full working space is the set of reachable points at the end of the robot when all poses are given. It can be obtained by the method of arc intersection. Its shape is an umbrella-like three-dimensional space, and the icon is W
The prerequisite for the definition of effective working space is the limit condition of the robot drive mechanism, which is the safety limit angle given by excluding the singular posture of the robot end and the interference of physical parts. Therefore, the effective working space refers to the maximum effective working area that can be reached at the end of the robot within the safety limit angle range. In order to intuitively reflect the effective working space, the figure is simplified as a cylindrical space combining a cylinder and a round table (icon D)
Considering the actual application of customers, the effective working space figure D defined in this article is mainly composed of 1 cylinder and 2 rounding tables (as shown in the figure above), and the rounding table shown in D3 is similar to an inverted cone. The end of the robot is in the effective working space D, which makes the overall rigidity of the robot as follows: in the horizontal direction, the rigidity gradually weakens when the point P is from the center of the base to the farthest point; in the vertical direction: the point P is from the center of the base to the farthest point. The rigidity gradually weakens at the lowest point. The difference in the structure of the actual parts of the robot leads to different degrees of weakening of the rigidity.
2. In actual applications, the pick and place span needs to be at least less than 20cm wingspan
Each company will give the robot’s range of motion, but if the robot is put into the actual integrated solution, relevant factors such as load, pick and place span, pick and place tempo, conveyor speed and other related factors are all important factors that affect the selection of the wingspan. .
The following figure is an example. The overlapping part of the working space of the robot and the working space of the conveyor belt constitutes the effective picking space of the integrated solution. The two items A and B located on the conveyor belt are located in different positions and stay in the effective picking when passing through the conveyor belt. The space and time are different. When the robot body has a smaller arm length, the conveyor belt picks up blind spots. A larger arm length also means a larger effective picking space.
3. Parallel connection has the advantage of more space and floor space, and large arm span can also be used at high speed
Compared with other industrial robots, the end-of-freedom and working space are not originally the areas that parallel robots are good at; and the larger arm span will inevitably restrict the movement speed of the elbow, and the production efficiency cannot be substantially improved; the practical scenes of the super-large arm span are mostly for handling. Heavy objects, extreme operating range, high speed, and high load have extremely high requirements for structural stability. These difficulties have been changed with the advent of D-2600 in January 2019. The super large arm span of 2600mm is the first in the field of parallel robots. .
The main body belongs to a customer-specific model and belongs to a 3+1 axis product series. It was originally established in November 2018 to solve the customer's need to reduce floor space. It took 2 months. Recently, the final in-house test phase was completed. In addition to the reach of 2600mm, the maximum pick-up height reaches 890mm, the standard beat (25-305-25 gate type trajectory) 120 times/minute, and the repeat positioning accuracy is ±0.1mm. It will be tested on the customer site soon.
In the case of a large arm span, as far as possible to ensure good performance of speed and load, Birkent Robot Research Institute has made new breakthroughs in mechanical structure. In addition to inheriting the original structural advantages of Birkent three plus one axis, inspired by the tenon and tenon structure of traditional Chinese architecture, the Robotics Research Institute boldly tried a composite fixed platform with high rigidity characteristics, which greatly improved the large reach structure Stability in operation avoids the problem of rigidity errors under high load and high-speed operation; integrated design of reducer and motor, light weight, small size, high rotation accuracy, and large torque; modular rotation unit for the fourth axis , Provide an effective solution for high-load and high-precision applications. The workpiece can be placed accurately without the need to design a secondary positioning device.
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