Hey friend,
One of the problems with humanoid robots is that they use a lot of energy.
Tesla Optimus, Figure 01 and Unitree G1 can walk well now but their batteries run out really fast. It is frustrating to see a humanoid robot take a steps and then need to be recharged. Especially when humans can walk for hours after eating a sandwich.
Today lets talk about the physics that can make humanoid robots use energy when they walk. We will start with the idea of walking and then look at some new ways to make robots walk more efficiently.
Why Humanoid Robots Use Much Energy
Walking on two legs is not very efficient compared to robots with wheels or four legs. Why is that?
- The robot has to work to stay upright and not fall over.
- Every step means the robot has to lift and move its body.
- The robot has to use energy to swing its legs and then stop them.
- When the robots heel hits the ground it can waste energy if it is not done correctly.
In the past humanoid robots used a lot of energy because they were stiff and made a lot of corrections to stay balanced.
Walking: A Smart Way to Walk
Nature found a way to walk efficiently a long time ago. This is called walking or passive dynamic walking.
The idea is simple:
When the robot swings its leg it uses gravity to do most of the work. The robot “falls” forward in a controlled way. Then uses a small push to start the next step, this is why walking feels easy once you get into a rhythm. We are using gravity and momentum to help us, not our muscles, some of the efficient robots ever built like the Cornell Ranger or Delfts Flame use this idea. They can walk with no energy on a gentle slope.
New Humanoid Robots Can Learn From This
Here are some ways that modern humanoid robots can use energy:
1. Using Natural Motion
of fighting the robots natural motion good controllers work with it. This is where flexible ankles and special actuators help a lot.
2. Storing and Reusing Energy
The robot can store energy when its heel hits the ground and then use it again when it pushes off. This can save 20-40% of the energy that would be wasted.
3. Finding the Way to Walk
This is the math part. Engineers use methods to find the best way for the robot to walk so it uses the least amount of energy.
4. Moving the Body
If the robot moves its arms and torso in time with its legs it can use less energy and walk more efficiently.
Whats Happening in the World
- Some research robots have gotten close to human levels of energy efficiency using special walking patterns and elastic actuators.
- Tesla Optimus has gotten better at walking efficiently over time partly by using its natural motion and reducing unnecessary corrections.
- Newer robots are using special actuators and planning to walk longer on the same battery.
My Thoughts
Energy efficiency is a problem for humanoid robots right now.
The exciting part is how many ideas come together to solve this problem:
- Using mechanisms and special actuators to save energy
- Planning the best way to walk
- Understanding how energy flows through the robot
- Using special methods to optimize the robots walking
- Learning from human walking data
I think the biggest improvements, in the 5-10 years will come from smarter use of physics not just stronger motors. When a humanoid robot can walk for hours on a charge while carrying a load we will know we have made real progress.