LibreServo is a project with the goal of easily converting any standard size servo into the smartest servo possible.

In the past (more than 10 years ago), I bought more than 20 5990TG servomotors from Hitec to build my second biped robot. They were expensive, with good hardware but still as dumb as the cheapest servo.
Years have passed and I always had a thorn in my side. Why not instead of dumb servos with excellent mechanics modify them to have clever servos with excellent mechanics? And, since we are going to design something new… why not make it in such a way that they would be compatible with future servos that I may buy?
The idea is to design the electronics of the servomotor to turn any standard servo into the smartest one in the world.
Text extracted from: https://www.libreservo.com/en/articulo/libreservo-objectives

Today, we shall talk about how [Adam Bäckström] took a DS3225 servo and rebuilt it to improve its accuracy, then built a high-precision robot arm with those modified servos to show just how much of an improvement he’s got – up to 36 times better positional accuracy.

https://github.com/adamb314/ServoProject

A tutorial on how to substantially increase your servos accuracy.

The video starts with a comparison of a regular DS3225 digital servo and one that has been modified. After that it shows how you can do the same modification.

Link to GitHub repository:
https://github.com/adamb314/ServoProject

Video chapters:
0:00 Introduction
0:19 Demo and comparison
1:39 Download the project
1:46 Order PCB
2:17 Burn bootloader
2:28 Print 3D parts
2:55 Modify the motor
7:23 Mount ITR8307 sensors
8:09 Soldering
9:37 Putting it together
12:14 Calibrating
16:04 Verify performance

How Servo Motors Work & How To Control Servos using Arduino
https://www.youtube.com/watch?v=LXURLvga8bQ

In this tutorial we will learn how servo motors work and how to control servos using Arduino and PCA9685 PWM driver.

This movie gives an overview of how RC servo motor works and how it’s made.

This video shows the mechanical construction of the servo.

Using an old servo as a generator, and supercapacitors for energy storage, this LED flashlight will last for decades. The original was built c. 2001, and still works fine in 2018! I

A few years ago, [patchartrand] decided to build a robot arm. The specs were simple: he needed a drive system that would be at least as strong as a human arm. After looking at motors, [patch] couldn’t find a solution for under $3,000. This led to the creation of the Ultra Servo, an embiggened version of the standard hobby servo that provides more than ten thousand oz-in of torque.

Your typical hobby servo has three main components. The electronics board reads some sort of signal to control a motor. This motor is strapped into a gear train of some sort, and a potentiometer reads the absolute position of a shaft. This is basically what the Ultra Servo is doing, although everything is much, much bigger.

Ultra Servo
https://hackaday.io/project/21332-ultra-servo

An ultra strong and fast servo that is reasonably priced. The goal is to generate 60ft*lbs (11 520oz*in) with 60 rpm no load rpm speed.

Description
Building anything that can interact with everyday life objects require high powered servos. This servo is intended to serve the maker ecosystem as to facilitate macro projects that interact with the world.

Specs:
60ft*lbs stall
60 rpm no load speed
Programmable angle range
6″ x 5″ x 3″ overall dimentions
12V or 24V operational voltage
TTL, SPI and Standard RC communications

The servo will be have a custom motor controller that will be Arduino based so anyone that needs to modify the parameters or so simply add functionality.