NovaKordo

Revolutionising robotic wrist movement …

… with a compact, cowerful, and versatile differential system

Introduction

Robotics enthusiasts and engineers are constantly looking for ways to improve the efficiency, compactness, and power of their designs. In this blog post, we will discuss a novel approach to creating a robotic wrist using a differential system, incorporating two servo motors and three beveled gears. This method offers a simple, compact, and powerful solution for maneuverability, while also providing precise positioning capabilities.

The Design:

The innovative design consists of two back-to-back servo motors, with their shafts aligned in a straight line. Each motor is equipped with a large beveled gear (A and B) attached to its shaft. A third beveled gear (C), of the same size but positioned at a right angle to gears A and B, is meshed between them. Activating the servo motors in opposite directions causes gear C to rotate along with gears A and B, resulting in a differential-like mechanism that drives the robotic wrist’s movement.

Benefits of the Design:

Simplicity: The design is straightforward and easy to understand, which makes it accessible to hobbyists and professionals alike. By using only three beveled gears and two servo motors, this solution simplifies the complexity of creating a robotic wrist mechanism.
Compactness: Due to its minimal components and clever arrangement, this design is highly compact. The back-to-back positioning of the servo motors saves space and allows the mechanism to be integrated into various robotic applications without taking up a significant amount of room.
Maneuverability: The differential-like action achieved by moving gears A and B in opposite directions enables excellent maneuverability for the robotic wrist. This design allows for a wide range of motion and flexibility, making it suitable for multiple purposes, from delicate tasks to robust applications.
Power and Precision: Utilizing servo motors in this design offers two distinct advantages: power and precision. Servo motors are known for their high torque capabilities and accurate positioning control, making them an ideal choice for a robotic wrist mechanism. The combination of powerful motors and the efficient transmission of force through the beveled gears results in a robust and precise system.

Conclusion:

This innovative approach to designing a robotic wrist using a differential system with servo motors and beveled gears offers numerous advantages over traditional designs. It is simple, compact, and provides excellent maneuverability, power, and precision. This solution has the potential to revolutionize robotic wrist mechanisms, opening up new possibilities for various applications in robotics and automation. Give it a try and experience the benefits of this ingenious design for yourself!

The above description was written by GPT4, and with the help of the video explains what I am trying to do although not why. You may have read elsewhere on the site that piano keyboard assemblies will be attached to the robot wrists and move (with instructions from sensors) so that however I move my hands, the keyboards will always be under the fingers. The original design using stepper motors worked moderately well, but needed a lot of improvement to be able to be used in a live instrument. I thought I would try this aproach too, and it seems quite promising. In the next stage I will introduce more powerful motors, better printed gears, and a slightly different arrangement that will allow greater movement.

How to make the gloves

Tech

Shopping list:

2 x BNO055 https://www.adafruit.com/product/2472
Teensy 4.0 dev board https://www.pjrc.com/store/teensy40.html
Wrist support gloves such as https://amz.run/6cQV
Velcro, staples, flexible wire, cable ties

I also 3D-printed housings for the electronics. I used this box for the Teensy from Thingiverse and adapted and printed 2 of these for the BNO055s. Contact me if you want my versions – they are not particularly good, but good enough for my need. In a later post, I will describe a better version that will work with the hand straps that I am now using.

On boxing the electronics, I attached the boxes to the gloves using Velcro, and to stop the Velcro from peeling off the gloves, I added some staples. I mounted one sensor to each of the “back of hand” parts of the left and right gloves, and the Teensy to the wrist of the right glove. Make sure you have enough wire to connect to the left hand so you can wave your arms around! The instructions for wiring the sensors to the Teensy can be found on the Adafruit site (or you can ask ChatGPT). Just to note that they both connect to the I2C bus so you need to change the address of one of the boards by linking the ADR pin to the 3V pin. Other than that it is 4 wires in total for Vin and Gnd and SCL and SDA for the I2C bus.

If you are going to program your Teensy 4.0 via the Arduino IDE you will need to add “Teensyduino” into the mix. These are the instructions you will need to do it. You will also need to configure the Teensy for USB midi.

Having done all this, the program is actually quite trivial and could probably be improved hugely. You will need to add the sensor and midi libraries to your IDE first. Once programmed your computer will recognise the USB as a midi device and you can add it to your DAW. I use Ableton and I set up 6 different choir voices to 6 different midi channels. Moving the hand will send different notes to different channels. How often the notes are played will depend on your hand position, as will the volume of the notes.

Once you get the idea, you could send out all sorts of data. Let me know what you come up with. In the next post, I will show you my next experiments in a gloveless arrangement and using midi CC data.

#include <Adafruit_BNO055.h>
#include <MIDI.h>

MIDI_CREATE_DEFAULT_INSTANCE();

Adafruit_BNO055 bno1 = Adafruit_BNO055(1, 0x28);
Adafruit_BNO055 bno2 = Adafruit_BNO055(2, 0x29);

// Set the base note and interval
const int notes[] = {43, 45, 46, 47, 49};

const int sopNote = 60;
const int interval = 7;

void setup(void)
{
  Serial.begin(115200);
  Serial.println("Dual BNO055 and Midi Test");  Serial.println("");

  // Begin MIDI
  usbMIDI.begin();

  if(!bno1.begin() || !bno2.begin())
  {
    Serial.print("Ooops, no BNO055 detected ... Check your wiring or I2C ADDR!");
    while(1);
  }
}

void loop(void)
{
  sensors_event_t event1;
  bno1.getEvent(&event1);
  sensors_event_t event2;
  bno2.getEvent(&event2);

   // Map the sensor data to MIDI values. The sensor data comes out between -180 and 180 
  // degreens and is mapped to one of  24 positions - my hands don't twist that much but it 
  // was convenient to do like this. To get one of 5 notes, I took modulo 5 so no other notes 
  // would be produced. Similar for the midi chanels

  int lhnote = notes[map(int(event2.orientation.x), -180, 180, 0, 24) % 5];
  int lhmidiChannel = map(int(event2.orientation.y), -180, 180, 0, 24) % 3 + 1;
  
  int rhnote = notes[map(int(event1.orientation.x), -180, 180, 0, 24) % 5] + 12;
  int rhmidiChannel = map(int(event1.orientation.y), -180, 180, 0, 24) % 3 + 4;

 int volume = map(event1.orientation.z, -180, 180, 0, 127);
 //   the z axis varies the delay between when notes are played in this loop
 int tempo = map(event2.orientation.z, -180, 180, 100, 3000);
 
  // Calculate the note a fifth apart
  int lhfifth = lhnote + interval;
  int rhfifth = rhnote + interval;

  Serial.print(F("Left: "));
  Serial.print(lhnote);
  Serial.print(F(" "));
  Serial.print(lhfifth);
  Serial.print(F(" "));
  Serial.print(lhmidiChannel);

  Serial.print(F("   Right: "));
  Serial.print(rhnote);
  Serial.print(F(" "));
  Serial.print(rhfifth);
  Serial.print(F(" "));
  
Serial.print(rhmidiChannel);
  Serial.print(F("    V: "));
  Serial.print(volume);
  Serial.print(F(" T: "));
  Serial.print(tempo);
  Serial.println(F(""));

  // Send the notes

  usbMIDI.sendNoteOn(lhnote, volume, lhmidiChannel);
  delay(10);

  // Send the note a fifth apart
  usbMIDI.sendNoteOn(lhfifth, volume, lhmidiChannel);

  usbMIDI.sendNoteOn(rhnote, volume, rhmidiChannel);
  delay(10);

  // Send the note a fifth apart
  usbMIDI.sendNoteOn(rhfifth, volume, rhmidiChannel);
  delay(tempo);


  // Turn off the note
  usbMIDI.sendNoteOff(lhnote, 0, lhmidiChannel);
  delay(10);

  // Turn off the note a fifth apart
  usbMIDI.sendNoteOff(lhfifth, 0, lhmidiChannel);
  delay(10);
  
  // Turn off the note
  usbMIDI.sendNoteOff(rhnote, 0, rhmidiChannel);
  delay(10);

  // Turn off the note a fifth apart
  usbMIDI.sendNoteOff(rhfifth, 0, rhmidiChannel);
  delay(500);

}

The gloves are on …

News

… and then they are off again! Last week, I gave myself 5 days to make a set of musical gloves that I would demonstrate at the weekend at UX Camp Brighton and with the help of ChatGPT I was able to pull off a fairly reasonable demonstration, even though I say so myself.

This week, the gloves came off and I made a Mark 2 version that had the sensors and the microcomputer attached to wristband replacements as used for fitness trackers. These seem like a better option for what I am hoping to achieve. In separate posts I will give all the info needed for one to build these yourself. In this post I am just going to talk about the rationale for doing this in the first place.

Anyone that knows anything about musical gloves will immediately think of Imogen Heaps’s Mi.Mu gloves which have orientation and gesture sensors, and also a means to detect finger motion. 10 years in development, these can be purchased for around £2500.

My gloves, in contrast, only have orientation sensors (BNO055) although it would be possible to detect gestures too. But the intention for mine is that whilst being able to send MIDI data for XY movements of the hand, that data will also be used to control piano keyboards attached to robot wrists that dastardly keep the keyboards under the hands in whichever orientation they might be. The rationale behind this is to allow accordion-like bellow movements without actually having bellows, and to control sound qualities other than volume (i.e. beyond simulating the pressure of air going through reeds).

I chose the Teensy 4.0 as the microcontroller for the project as I had used it before when I made a joystick to midi controller. The Teensy is an Arduino-like board with the advantage that it configures very nicely for USB midi and can be programmed from the Arduino IDE. Despite the fact that I had used the technology before, I got ChatGPT to write me a program for testing the midi interface.

For the position sensors, I chose BNO055 boards from Adafruit. Using a chipset from Bosch these boards give 9 degrees of freedom (9DOF) with XYZ outputs for position, acceleration and magnetic field. I was just going to be using the position data. I had some experience with these sensors too, having played with them for getting motors to move (in advance of building the robotic wrists). But once again I found it useful to get ChatGPT to write me some test routines. (It literally is just asking ChatGPT to write the program, pasting it into the Arduino IDE, compiling and uploading the program to the Teensy and then checking the output in the “Serial Monitor”.

Having established both the midi and the sensors were working, it was now just a question of mounting the sensors onto gloves (elasticated and fingerless orthopaedic £5 purchase from Amazon) using Velcro. I didn’t want a “beepy” electronic noise for my demo so I chose a choir plugin from Spitfire Audio. The left hand was going to play one of 5 notes from D, E, F, G and A from the tenor and bass samples, plus a note a 5th above. The notes chosen would be dependent on the x-axis rotation of my hand, and similarly the alto and soprano samples with my right hand. Choosing this combination would hopefully give a relatively pleasing sound whatever the combination. To get some tonal variation, the choir plugin allows you to choose between short and long sounds and I put these on different midi channels, which were selected by the y-axis position of my hands. I should add that this was done in Ableton Live. I should also add that ChatGPT pretty much wrote the whole program for this too – although my commands here were to add routines to what I already had

To add more variation, I was able to control the volume with the z-rotation of my right hand, and the frequency with which the midi notes were sent out with my left-hand z- position. Finally, I added a little random percussion using Dillon Bastan’s “Inspired by Nature” free sound pack. I had just been watching this demoed on this excellent YouTube video by ELPHNT.

Surprisingly, it all worked rather well as you will see in the video below, and also at my session at UXCamp. To say that I was completely in control of what I was playing would be wrong – let’s just say that the slight randomness of sound to hand gestures rather added to it’s appeal.

This is all getting a bit to TL:DR so I will save the bit about the mark 2 gloveless version for the next post, but here is the gloves-on version.

A grand piano attachment

News

What do you do with a piano that refuses to stay in tune and is too expensive to repair? My piano tuner said it would cost around £5000 to recondition and the best option was to replace it. I was tempted, but I was more than happy with my Roland FP7 and the Pianoteq plugin. I decided to strip the piano out and use the “box” as a box – a container for the electronics associated with my synth setup.

Things of possible interest are the foot – made to look as though it runs right through the case, it is, in fact, a bit below and a bit above. The tubes came from Jaspers, from where I got most of the other bits, and I 3D printed the black plastic bits into which the tubes are inserted. The number of people who come around and instantly want to lean against the case – a bad idea as the case is just resting on the foot. Possibly should change this at some point.

I like to have the lower keyboard raked down slightly and this worked out well as I was able to make a joint that both allowed for this and provided a way of attaching the piano box to the rig. The weight of the box is counterbalanced by the weight of the keyboards etc. In the picture below, you can see the adjustable joint I created, and also the point of attachment to the box – basically just a big nut and bolt.

Whilst not actually to do with the Novakordo, I thought it might be of interest, partly because it is sort of another musical invention, and because I was watching a Maker’s Muse video on attaching anything to anything else.

The story

home

I love the piano accordion. After playing the piano from childhood, I bought my first accordion after I moved to Brighton, UK in 1998. Unlike most musical instruments, when you hug the accordion to your body you become a portable one-man band. On your right, you have a piano keyboard for melodies, and on your left a combined bass section and chord generator beautifully arranged as a matrix of up to 6 x 20 buttons (and when I say beautiful, I should say extraordinarily beautiful). And if this wasn’t enough, you power this contraption with a set of bellows that enables a wonderful degree of expression by controlling the air passing through the reeds which make the music.

It was inevitable that someone would one day create an electronic version of the instrument as surely as the computer keyboard followed the typewriter. The one I have has the virtue of allowing me to play a world of different accordions from the Parisien musette to the bandoneons of Buenos Aries. And on top of this, mine comes kitted out with Hammond organ, Fender Rhodes and many other sounds common on standard electronic keyboards. The bellows are still there but instead of the air being forced through reeds they produce a voltage proportional to the squeeze and control the volume almost (but not quite as well) as effectively as the acoustic instrument. The irony is that I wanted a portable instrument that I could carry as I got older and more decrepit – the one I have now weighs more than a modern keyboard and you cant stick it on a stand – you have to wear it!

But …

Replicating an accordion electronically doesn’t truly expand its versatility into the 21st century. Freed from the need for a mechanical interface to open and close valves how can we add a keyboard in an ergonomic way? Bellows allow volume control but is this just hot air (only on a summer’s day) and could we have a better expression controller? Buttons, buttons, buttons. Everyone is using buttons now from drum programmers to “push” controllers but is there a way to combine the sophistication of the accordion button board with something more? Or to put that together, can I make my one-man band a one-man orchestra?

Welcome to the Novakordo. There are four main parts to the instrument (in Esperanto, Novakordo means “new chord”) the frame, the robot wrists, the keyboards, and the button boards.

The frame

I tried many ways to hold all the components together, and although I like the idea of something wearable, such as a waistcoat, my current best fit is a tubular construction that is strapped to the body with straps – I found that a back-posture corrector is nearly ideal – other than you need to climb into it which is difficult (but not impossible) without an assistant. By having this setup, one can add other modules as one wishes. For example, I plan to add a breath controller and microphones at some stage. To support the main modules, I have incorporated a robust dual mount (intended for video displays) and the modules are mounted at both ends. I have 3D printed many of the components that create the frame (and other parts of the Novakorda). I am making public all the files for printing (and everything else) so that others can make or modify what I have done. Oh, and did I mention, the frame lights up?

I did build several button boards that adapted a traditional accordion button board but moved in the direction of typewriter to computer keyboard. Whilst I may progress this again in the future, currently, I am playing with a Novation Launchpad Mini (from here called the Pad). This allows me to use the buttons as accordion keys (with programming in Max for Live) or for launching clips from Ableton. It is worth pointing out that all the musical sounds that are heard are generated within the computer and under the control of Ableton. If one had large hands one would be able to reach all parts of the pad easily. With smaller hands (me!) I have created a slider with thumb support that allows movement to all buttons. The slider/support has another function which is to move the board around as …

… just as the left hand on the accordion plays the buttons and controls the volume by moving the bellow, the left hand on the Novakordo plays the buttons and controls the expression by physically moving the Pad. And here’s the clever bit, this occurs because the Pad is mounted on a joystick giving it 6 degrees of freedom: up-down, left-right and rotating clockwise-anticlockwise. The joystick is connected through a small computer (the Arduino-like Teensy 4) and outputs 3 midi control signals that can be used in a variety of ways. The possibilities are endless but here are some serving suggestions:

One parameter is volume – or as programmed in Max a means of mimicking bellows – so without any movement you get no sound. The volume increases proportionally to the speed and accelerating movements will give a percussive effect.

The second axis could change the sound of the instrument between say a flute and clarinet (and don’t forget the midi controller can be applied to either the keyboard or the button board or both),

The third axis could control the speed of a Lesley speaker, pan sounds from one side of the room to the other, set the rate of echo, or control an arpeggiator or …

I’ve worked as a biologist, musician, truck driver, taichi teacher, computer scientist for the European Space Agency and serial inventor.

I created a synthesiser before they “existed”, built an early polyphonic synth when they were mainly monophonic, and made music programs before the age of the PC.

After many years of making educational games for children, I have gone back to music, both as a performer and as an instrument creator.

Having started playing the accordion 20 years ago, I wanted to do for that instrument, what technology has done for the typewriter. And then learn to play it.

The intro

home

This website describes a new instrument that has its roots in the accordion, a musical instrument invented* in the early 1800s and has not undergone significant changes until now. **

On the following pages, I will tell the story of how I came to create the instrument, provide news as to how I am developing Novokordo (the name comes from Esperanto meaning “a new chord”), and provide details and files of all the components so that anyone can build there own, modify it for their own performances, and generally improve the design.

There are also videos of me playing the instrument, and details of performances, both solo and with one of the bands that I play in, Psychospherix. Plus there will be information on how I will be using Novokordo in my Carla Bley project (core name SexGlo) to be performed in September 2022.

*Some credit Friedrich L. Buschmann, whose Handäoline was patented in Berlin in 1822, as the inventor of the accordion, while others give the distinction to Cyril Demian of Vienna, who patented his Accordion in 1829, thus coining the name.

**One might mention melodions, concertinas and bandoneons as developments – but my ideas go beyond having to use bellows, and lie strictly in the realm of the electronic. (I can absolutely bet that someone, somewhere has created something electronic that I haven’t heard of: watch this space!)