Thermal Design robot manipulator

    Robot is an automatic machine that can replace human beings to engage in dangerous and complex labor in unstructured environment. It is a complex of machinery, electronics, software and perception. It is different from consumer products. There are many robot parts. If the preliminary scheme is not fully considered, it will often consume a lot of human and material resources, and sometimes lead the whole body. Therefore, in the early development process, it is necessary to use reliability methods such as mechanical design, thermal design and fluid analysis to avoid risks, reduce the number of proofing and shorten the development cycle.

Heat Dissipation Requirement:

   As shown in the legend, due to the limitation of structure and volume, 7 drive control modules need to be integrated on the development manipulator body, and each drive control module controls a motor. The drive control module is an aluminum substrate, which is a metal based copper clad laminate with good heat dissipation function; The temperature resistance of the aluminum substrate (TS) of the drive control module is 85 ℃. When the temperature exceeds 85 ℃, the drive control module stops working. The official recommendation is that TS ≤ 80 ℃. This manipulator is applied to medical robot products. The maximum temperature of the robot working environment is 25 ℃, which has strict requirements on the shell temperature. Seven motors work at the same time: 10s ≤ t ≤ 1min, and the maximum temperature needs to be ≤ 51 ℃.

Pre-phase Analyses:

The drive control module is an aluminum substrate, so the drive control module needs to transfer heat to the structure through a thermal pad . According to the previous calculation, forced air cooling is required in the limited space to ensure the overall heat dissipation requirements; There are two ways to plan heat dissipation:

 1. Seven drive modules are pasted on a heat sink, and the heat sink + axial flow fan + mechanical arm shell is designed for air duct; The thermal conduction path of this design is as follows:  drive control module → thermal pad → heat sink → air in the cavity (forced convection) → cavity shell → air outside the cavity (natural convection + thermal radiation). However ， In this design, the air in the cavity can not be directly connected with the outside air, and there is a great thermal resistance in the middle, lead to the bad thermal performance.

2. The seven drive modules are directly attached to the shell of the manipulator, add fin design to the shell of the manipulator, the axial fan is installed outside the shell of the manipulator, and a cover plate is added for air duct design.

Thermal Simulation:

  Using smart simulation software to simplify the module and proceed the thermal simulation analysis the data.

  According to the thermal simulation temperature cloud diagram of the shell, the position with higher shell temperature is on the right side, the upper shell max = 44.9 ℃, min = 42.35 ℃, and the aluminum substrate of the drive control board max = 47.6 ℃, which meets the design requirements.

    Through thermal design analysis, engineers can have a deeper understanding of how thermal design is integrated into structural design in the early stage of design, and this idea can be used for reference in the subsequent design process to guide structural design. At the same time, thermal simulation can quickly find the deficiencies in the design and optimize the design direction.