tailieunhanh - Industrial Brushless Servomotors Episode 8

Tham khảo tài liệu 'industrial brushless servomotors episode 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Motor and load dynamics 135 The reflected inertia of the load mass should be matched with the inertia which already exists on the motor side of the screw threads and so J Jm Aw where Jsw is the inertia of the screw. Combining the last two equations and including the effect of force F gives the optimum screw pitch as 2ir dm fw . A I where A2 ZMv I 2 p 2 Ft2p xm d is the optimum screw pitch when the load follows any trapezoidal velocity profile and is subject to an opposing force. Figure Two-axis pick-and-place handling machine. Photo courtesy of Hauser division of Parker Hannifin Example The sinusoidal motor in Table is to be used to drive a ball screw. The load velocity is to follow the profile shown in Figure . The system constants are 136 Industrial Brushless Servomotors Jm kgm2 Jsw kgm2 X m tp s F 1000N m 5 kg The profile constant is Cp p P2 1 1 pi 4-P2 2 In this case Pi 20 120 and P2 60 120 giving Cp 18. The load force factor is . 1 1000 X 2 is 002575 737 The optimum screw pitch is fl A 27Tị V 5ựl 737 mm In this example the optimum pitch is dictated mainly by the effect of the load force. In the hypothetical case of zero load force the optimum screw pitch given by the calculation would be d 44 mm Figure Load velocity profile for example Motor and load dynamics 137 Torsional resonance In Sections and the mechanical connection between the motor and load is assumed to be inelastic leaving the increase in system inertia as the only mechanical effect of an added load. In practice some flexibility in the connection is unavoidable and an error may develop in the position of the load relative to that of the hub of the rotor of the motor as torsional forces come into play. When the error becomes oscillatory the condition is known as torsional resonance. The problem can also arise in the section of shaft between the hub and the sensor but we will assume throughout