Electrohydraulic Robot Joint Drive With Variable Pump Capacity
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Solution Overview
Problem
Existing articulated robots face challenges in achieving desired movement at joints due to varying torque and speed requirements, which are not adequately met by traditional electric motor-driven systems, leading to insufficient performance depending on the posture of the manipulator.
Innovation Solution
An electrohydraulic robot system with a manipulator and drive devices, each comprising a hydraulic actuator, a variable capacity hydraulic pump, and an electric motor, where the control device adjusts the discharge capacity of the pump to control torque and speed, allowing for focused drive-force or speed movements at each joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the speed reduction ratio of the speed reducer is set high, then the torque for joint movement is increased, but the speed for joint movement is reduced
Solution Approach 1:
The patent applies dynamics by making the speed reduction ratio variable rather than fixed. The control device dynamically adjusts the speed reduction ratio of the hydraulic speed reducer based on real-time requirements for torque and speed at each joint, allowing the system to adapt between torque-focused and speed-focused operation modes as needed
Solution Approach 2:
The patent changes the parameter of speed reduction ratio from a constant value to a variable parameter. By controlling the discharge capacity of the hydraulic pump, the system varies the speed reduction ratio to match the varying torque and speed requirements at different joint positions and operational phases
2Speed
If the speed reduction ratio of the speed reducer is set low, then the speed for joint movement is increased, but the torque for joint movement is insufficient
Solution Approach 1:
The system dynamically adjusts the speed reduction ratio based on real-time torque and speed requirements. When high speed is needed, the control device lowers the speed reduction ratio, and when high torque is needed, it increases the speed reduction ratio, allowing optimal performance in both regimes
Solution Approach 2:
The speed reduction ratio is changed from a fixed parameter to a variable parameter controlled by the discharge capacity of the hydraulic pump, enabling the system to provide sufficient torque at low speed reduction ratios and high speed at high reduction ratios as conditions require
3Power
If the size of the electric motor is increased to meet varying torque and speed demands, then the torque and speed requirements are satisfied, but the device complexity and cost increase
Solution Approach 1:
The patent replaces the direct electric motor-drive system with a hydraulic transmission system. The electric motor drives a hydraulic pump that supplies pressurized fluid to hydraulic actuators, which then drive the joints. This hydraulic intermediary enables flexible torque and speed control without requiring a large, complex electric motor with variable capacity
Solution Approach 2:
The hydraulic system acts as an intermediary between the electric motor and the joints. The hydraulic pump and hydraulic actuators serve as intermediate components that transform the motor's rotational output into the required torque and speed at each joint, simplifying the overall system while maintaining full control capability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables desired movement at each joint by adjusting the hydraulic pump's discharge capacity, reducing the need for large electric motors and improving work efficiency by matching torque and speed requirements dynamically.
Implementation Method 1
a hydraulic pump of a variable capacity type that supplies a working fluid to the hydraulic actuator
Implementation Method 2
a hydraulic actuator that moves a corresponding one of the plurality of joints
Data Source
AI summary
This electrohydraulic robot includes: a manipulator including a plurality of joints; a plurality of drive devices that are provided in a one-to-one correspondence with the plurality of joints and each move a corresponding one of the plurality of joints; and a control device that controls movement of each of the plurality of drive devices. Each of the plurality of drive devices includes: a hydraulic actuator that moves a corresponding one of the plurality of joints; a hydraulic pump that supplies a working fluid to the hydraulic actuator; and an electric motor that drives the hydraulic pump. The control device is a pump of a variable capacity type that drives the electric motor and changes the discharge capacity of the hydraulic pump.