General Information Regarding Reaction Forces and Moments for a Robot

Question 1:

How do the reaction forces (Fh and Fv) and moments (Mh and Mv) that are listed in each robot manual’s installation chapter affect a base structure? Do they occur all at the same time or only one at a time?

Answer 1:

When designing base structures, it is recommended to analyze the design using the Mh and Mv moments along with the robot’s mass. The Mh and Mv moments that the base structure receives from the robot are applied where the robot mounts. The only force to consider for the base structure is the robot mass at the robot mounting position.

For the analysis, acceleration/deceleration moments are cyclical. Emergency stop moments are singular, sporadic events and are to be analyzed as such. It is recommended to evaluate the Mh and Mv moments separately, as it is not possible for the combined moment values to occur simultaneously.

Question 2:

Has Yaskawa already applied a safety factor to the reaction forces/moments? Should a customer add additional safety factors?

Answer 2:

Customers do not need to add additional safety factors to the published reaction forces/moments values. Customers are responsible for their own design criteria on allowable structure stress and fatigue.  

Question 3:

What is the load that occurs during a robot crash? Is it greater than the reaction forces/moments?

Answer 3:

A robot crash will not have moments exceeding the emergency stop Mh and Mv values.

Question 4:

The installation manual only mentions bolting to a riser/foundation. Does Yaskawa have any guidance for mounting scenarios that include mobile unpowered carts (or mounted to an AGV)?

Answer 4:

There is no official manual information about mobile carts or AGV’s, so it is fully up to the customer to analyze the risks. The recommendation is that the mounting bolts have adequate thread engagement to the cart and are torqued according to the installation chapter of the specific robot. The cart’s dimensions must be wide enough and/or the cart must be heavy enough that the robot can never tip the cart over with an extended posture. At a minimum, the CG of the combined assembly must be within the wheels or contacts with the floor. Max robot posture CG must be considered when evaluating the tipping point.

Question 5:

Does the height of the robot mounting structure have any impact on the values in the manual?

Answer 5:

The height of the robot mounting structure does not alter the reaction values in the manual. However, moments must be applied where the robot mounts to properly evaluate the structure.