# How to ensure maximum possible joint torque for an actuator?

• TheShermanTanker
In summary, the conversation discusses attaching a linear actuator on a moving arm in a joint system with a fixed anchor. The goal is to have the mechanical advantage of the actuator be exactly 1, meaning it only needs to generate enough force to balance the load on the moving arm. However, there is a necessary constraint that the other end of the actuator must be fixed to the fixed arm and be as close to the moving arm as possible. This poses a problem because the torque generated depends on the perpendicular distance to the pivot, and fixing the actuator further out still puts it at a mechanical disadvantage. The conversation concludes with a discussion on how to solve this issue and the difference between constraints and optimization goals.
TheShermanTanker
Below, I have a joint system that consists of a fixed anchor and a moving arm:

What I want is simple: To attach a linear actuator on the moving arm in such a way that the mechanical advantage of the actuator is exactly 1 (Ie the actuator only has to generate exactly the amount of force as the load on the moving arm)

This may seem simple at first glance, just attach the actuator at the far end of the moving arm, right?

But there is a necessary constraint: The other end of the actuator has to be fixed to the fixed arm AND has to be as close to the moving arm as possible, I can't just stick the other end to anywhere I want. So now I end up with this:

The problem is that torque generated depends on perpendicular distance to the pivot. So no matter how far out I fix the actuator, it's still at a mechanical disadvantage, since the actual perpendicular distance to the pivot is very small

Anyone know how I can fix this issue?

Why not just fix the actuator to the moving arm? It just needs to push the load straight away from the end of the moving arm, right? Why does this force need to be transferred to the fixed arm through anything but the pivot bearing?

I guess I'm not understanding your problem statement so far...

TheShermanTanker said:
But there is a necessary constraint: The other end of the actuator has to be fixed to the fixed arm AND has to be as close to the moving arm as possible,
That's not a constraint, but an optimization goal.

TheShermanTanker said:
I can't just stick the other end to anywhere I want.
That's an ill-defined constraint.

TheShermanTanker said:
(Ie the actuator only has to generate exactly the amount of force as the load on the moving arm)
That's a constraint.

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## 1. What is joint torque and why is it important for an actuator?

Joint torque is the measure of the force or moment that an actuator can exert on a joint. It is important because it determines the maximum amount of force that the actuator can apply to move the joint.

## 2. How can I calculate the maximum possible joint torque for an actuator?

The maximum possible joint torque for an actuator can be calculated by multiplying the actuator's maximum output force by the distance between the actuator and the joint. This will give you the maximum torque that the actuator can generate at the joint.

## 3. What factors can affect the maximum possible joint torque for an actuator?

The maximum possible joint torque for an actuator can be affected by various factors such as the actuator's size, power source, gearing, and friction. The type of joint and its range of motion can also impact the maximum torque that can be achieved.

## 4. How can I improve the maximum possible joint torque for an actuator?

To improve the maximum possible joint torque for an actuator, you can increase the actuator's power source, use a larger actuator, or add gearing to increase the output force. Reducing friction in the joint can also help to improve the maximum torque that can be achieved.

## 5. Are there any limitations to the maximum possible joint torque for an actuator?

Yes, there are limitations to the maximum possible joint torque for an actuator. These limitations can include the physical properties of the actuator, such as its size and power, as well as the mechanical limitations of the joint. Additionally, safety considerations and the load capacity of the actuator should also be taken into account when determining the maximum possible joint torque.

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