Delta Bot Plucks Out Tunes on a Mandolin

Is there no occupation safe from the scourge of robotic replacement? First it was the automobile assemblers, then fast food workers, and now it’s the — mandolin players?

Probably not, unless [Clayton Darwin]’s mandolin playing pluck-bot has anything to say about it. The pick-wielding delta-ish robot can be seen in action in the video below, plucking out the iconic opening measures of that 70s prom-theme favorite, “Colour My World.” The robot consists of two stepper motors connected to a hinged wooden arm by two pushrods. We had to slow the video down to catch the motion, but it looks like [Clayton] has worked out the kinematics so that the pick can be positioned in front of any of the mandolin’s eight strings. A quick move of the lower stepper then flicks the pick across a string and plucks it. [Clayton] goes into some detail about how he built the motion-control part in an earlier video; he also proves that steppers are better musicians than we’ll ever be with a little “Axel F” break.

It’s only a beginning, of course, but the complexity of the kinematics just goes to show how simple playing an instrument isn’t. Unless, of course, you unleash an endless waterfall of marbles on the problem.

Thanks for the tip, [baldpower].

22 thoughts on “Delta Bot Plucks Out Tunes on a Mandolin

    1. What is Arc Delta? This is 2D and the curved parts can be straight and it works the same doesn’t it? Or is it because of the extra lever? It seems that is similar, but less complicated than the platform at the end of a delta?

      1. I believe the arc part refers to how the motors rotate an additional linkage in an arc rather than a linear actuator like you usually see on delta printers–where belts or screws move three carriages vertically, to which are attached the arm linkages.

    2. Linear Cartesian Series Kinematics: (Prusa configuration) This is your standard 3D printer. The Stepper motors movement is converted to a linear motion by a belt. Motions are in series and only the last of the series is connected to the end effector. The kinematics are simple. xSteps = x * xConstant; ySteps = y * yConstant; etc

      Linear Delta Parallel Kinematics: (Kossel configuration) Once again belts are used to convert the rotation of the steppers to a linear movement. All 3 steppers move the end effector in parallel rather than series. The kinematics is more complex, lots of cos() and sin() and the equations are no longer independent as any one stepper effects x, y and z

      Arc Delta Parallel Kinematics: The motion of the steppers remains rotational (arc). The kinematics is even more complex. Often used in industry for it’s speed.

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