Our first Robot Arm controller

Firstly we would like to apologize for the delay in having our products available; this has been due to switching over to lead free solder in our surface mount process.  Lead free solder past requires a significantly higher temperature in the reflow process and this caused some problems.  This has been resolved and we should have all our currently listed products available at the start of January.

We are currently building and programming our first motor control module.  In a previous blog I mentioned the options we had for a dense motor control module.  All along we wanted to be able to control a full blown robot/cobot arm, not a toy, but a real working robot arm with a reach of up to 6 ft (2m) and able to lift 10 lbs (4-5 Kg).  A lot depends on the mechanics of the arm, but we feel we have the power in the electronics to do it.  Basically we will have 5 x 3.1A stepper driver channels with homing inputs, and 6 x PWM servo channels with current (force) sensing working as an extender module to a controller module.  It will be available in a month or so as a 3 stepper channel and 6 servo channel version with 2 more steppers channels as an option (all channels internal).  The stepper drivers can operate from 10V to 35V and have a separate power connector (the module itself requires from 10-28VDC).  The advantage of a higher stepper voltage is speed.  Eventually the stepper motor speed is limited by its inductance, which resists the increase of current flow when the motor steps and coil current starts.  The higher the voltage the faster the current can increase to the maximum current set.  We have used the TMC5150 stepper control chip in the module which is known for its 256 step sine wave silent operation coupled with 40A mosfets.

Of course, as planned from the start, all of our motion control products will have multi-axis synchronization, within a module, and across multiple modules of many motor types totaling up to tens and tens of axes.  They are not synchronized down to the step, but are synchronized at the vector level making them ideal for robotics but are not really intended for most CNC applications.  The motion is very smooth, being synchronized in S curve acceleration/deceleration and constant speed phases, and starting and stopping with microsecond precision. Five stepper axes provides for shoulder, upper arm worm drive joint and possibly an elbow worm drive, and an elbow, wrist swivel and wrist elevation stepper/harmonic drive, leaving six force sense servo channels for the manipulator.  The 3 stepper base version of SmartArm2 is expected to be well under US$300.

In 2024 we will develop a reference design robot arm and software to greatly simplify splitting the single destination vector into the many individual axis vectors for a robotic arm.  One of the easiest ways to teach an arm is with a pendulum or multi axes hand controller input device that has multiple axes sensor/switches to make the wrist/manipulator follow your motions.  The directions can be split into larger destination points, or have the complete motion be periodically split into smaller steps.  Because of the synchronization it is usually better to have fewer but larger vector points to avoid the corrections made by human guidance over a long vector.

Having set the maximum acceleration and top speed for a channel it is a simple matter to define the multiple axes destinations for a synchronized motion and the driver software in the library will workout the individual accelerations and top speeds for each axis and pass them to ChamNet to send to the appropriate modules and channels.  You get an event message when the motion modules are ready for another set of vectors (a few vectors can be chained in the modules buffer).

In 2024 we will also bring motion modules to control DC actuators with potentiometer position feedback, DC motors with quadrature encoders, and 3 phase motor drivers with quadrature or phase feedback, all with integrated drivers.  Our 7” capacitive smart touch screen will also be introduced early in 2024.  This will be a front panel mounting module that can house two of our module PCB’s, usually a controller and an extender.  The touchscreen is ‘programmed’ using a PC app that allows multiple panes of drag and drop widgets like gauges, buttons and sliders.  Your code sends and gets values to and from the named widgets. A sound module allows you to trigger .wav ‘sound bytes’ from an SD card you can insert in the bottom of the module.  We expect to incorporate sending and getting widget values into ChamNet write and event messaging to avoid polling the serial port that the module uses.  Sign up for emails or keep checking the website for the release of SmartArm2 and SmartScreen7 in 2024.

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