Trajectory Planning for Energy Optimization

Abstract

Energy optimization is important for economic justification besides several motion constraint parameters such as cutting tool travel distance, speed and acceleration during the machine operations. These parameters are important to avoid excessive vibration, work piece breakage and machine tool fatigue for long period time of usage. Thus, tracking energy consumption under motion constraints is essential. To track the motion of DC motors, simple trajectory motion is expressed in terms of a trapezoidal velocity profile. This is because trapezoidal velocity profile is widely used in industrial machines in particular for point to point motion. The motion is tracked by the encoder to detect the position of the motor and then differentiate it to make it a trapezoidal velocity profile and acceleration profile. The challenging issue is to utilise the concept of energy optimization with the setting up of a limit speed. Cutting machine tools and rotary cranes are great examples to apply the concept where a certain speed of cutting tool or rotary crane is the limit to avoid overheating and excessive vibration as well as at the same time to include the energy analysis for the machine, especially on the actuator. The electric motor can be viewed as the most common actuator used worldwide compared to other types of actuators such as hydraulic, pneumatic, electrolysis etc. Objectives: The objectives of this paper are to propose, simulate and analyse energy optimization method based on a trapezoidal velocity profile. Methods: Based on trapezoidal trajectory planning, there are two situations conducted for energy optimization. The first situation is concentrating energy optimization based on fixed parameters for total motion distance and varied parameters for maximum velocity. The second situation is where the total motion distance is not fixed anymore and maximum velocity is the fixed variable. Therefore, the study conducted for this paper is to find the energy consumption and to compare the interpretation of energy optimization for those two situations. The prototype used in this paper is under actuated crane mechanism which consists a double link system where rotation motions consist of two parts, each belonging to respective links. Link 1 is a rotation motion due to the DC motor embedded with the encoder. Link 2 is the swing motion affected by link 1. Results: The analysis of results for the two situations is discussed in two sections as follows • Energy consumption for fixed total motion time. • Energy consumption for fixed maximum/constant velocity Two situations of trajectory planning of trapezoidal velocity profile were compared and interpreted with respect to the energy optimization. The results of this paper show that energy utilization on rotary robot cranes can be optimized with different velocity profile parameter constraints. The energy consumption at different acceleration times was analysed and optimised. Conclusions: The results show that the energy consumption can be optimised with respective to two situations above.