I have a customer in Lithuania (Europe), a company which wants to automate / retrofit many different metal working machines. They would like to find logical, optimal way of motion control and follow it later on. It is clear that they want to use a closed loop control type. They started and made quite a lot of mechanic works. There are pneumatic, hydraulic things to control and a need for motors, of course. The company is ready to find a supplier from China (as an example) and cooperate with it.
As for the controller, I am thinking of LinuxCNC on a PC. And maybe something embedded like Raspberry Pi later on. The question is: which way to go? I mean I can choose from: 1. Take AC servo motors and drives like Yaskawa, Panasonic, Delta electronics, add gearboxes, tune PID, use position control mode using LPT and step/dir. 2. The same as 1, but with mesa card and velocity control mode, position loop in LinuxCNC. I think this way is logical only where trajectory following needed. 3. Some much simpler DC brushed servo motors and drives, power supply, gearboxes, tune PID, LPT, step/dir. 4. Closed-loop stepper systems, power supply, tune PID, LPT, step/dir and at-position input. I mean smth. like http://www.leadshine.com/Product_Show.aspx?ID=22 + http://www.leadshine.com/Product_Show.aspx?ID=185 . By the way, I am thinking of this method very much, because I like the way they work http://www.youtube.com/watch?v=ZMZdCcLQc4M . And there is no need for the gearbox. 5. DC brushed or BLDC servo motor and some available or own-made amplifier with dir/pwm or dir/analog or +-10V analog to control current, some LinuxCNC compatible card and LinuxCNC to close the position loop. As for the 5th, I think it is possible to use a bridge, make PWM frequency booster or serial-in to PWM-out controller with current limiter and encoder counter with serial shift-out interface. Don't know brushed or brushless. I have designed a controller for a BLDC motor up to 50V, using Allegro A3930. Could adapt it to serial-in or dir + PWM-in current control. Thought about using RC-hobby BLDC motors, add encoder to it (rotary magnetic encoder IC possible where good accuracy is not needed) and use as a servo with LinuxCNC. Which way would be the best, what would you suggest? I think using MESA cards on a machine with only one or two servos for positioning is not economically practical. Some more tech. details. Most of the tasks need more force than speed or acceleration. Forces needed are in 10-65 kgf range, most of them are about 25-30kgf. Acceleration forces are much smaller. Accuracies: 0.2-0.5mm, and a better ones for small lathe machine with revolver tool changers. Speeds: 100-500 mm/s, mostly 100-300mm/s I think and smaller for the lathe. Type of work: position and stop, then do something else, etc. Except for lathe, where trajectory following is needed. Some of tasks require very little of user interface. Some programs may be entered and started from a limited list later. I made calculations which say that 200W motors are enough for most of the tasks. I have quite good knowledge of LinuxCnc, but never used MESA cards or similar ones yet. I do program micro-controllers in C (did 8 bit AVR's mostly). I design and build electronics by myself (designed some motor controllers, latest project: powerfull BLDC controller), run CNC machines, use and program in CAD, CAM systems. I am an IT engineer by profession. By the way, I am finishing to collect preliminary prices of products for 1st, 3rd and 4th variants. ------------------------------------------------------------------------------ Own the Future-Intel(R) Level Up Game Demo Contest 2013 Rise to greatness in Intel's independent game demo contest. Compete for recognition, cash, and the chance to get your game on Steam. $5K grand prize plus 10 genre and skill prizes. Submit your demo by 6/6/13. http://altfarm.mediaplex.com/ad/ck/12124-176961-30367-2 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
