Motor Control Systems – Bode Plot & Stability


Set point feedback controller

What is a control system? A control system alters the future state of its system to a more desirable outcome. We often work with feedback control systems (also called closed-loop control), where the result of the command is fed back into the control system. In particular we are looking for the error between the command […]

How to Mount an External Removable Hard Drive on a Robot


fstab options for mounting drive

We often want to add an external hard drive to our robots in order to have a dedicated drive for data collection. Having the dedicated drive lets the primary drive remain uncluttered, have less wear-and-tear, split logging between drives for performance, and potentially be a larger spinning disk (as opposed to an expensive SSD). It […]

Bearings, Bushings & The Engineering Commons


I listen to several podcasts, including The Amp Hour, Embedded, and the Engineering Commons. A recent (depends when you read this) Engineering Commons podcast was all about bearings. I have been wanting to write a bearings post for a while so I am using their podcast (with permission) as a basis for writing this post. […]

Tether’s: Should Your Robot Have One?



Some people swear that all tethers are bad. Some people recommend attaching a tether to robots in order to provide power (to save the mass and volume of the batteries), for reliable fast communications, transfer of pressure or fluid, to track a robots position, or as a safety harness (in case the robot needs to […]

Drive Selection – Wheels, tracks and more


Marsokhod 6x6 is completely articulated in pitch, roll and yaw.

In the past we have looked at wheel design and the kinematics of skid steer and mecanum wheels. In this post we will take a quick look at different types of mobility types (ie. wheels, tracks, and how to connect them) for drive selection. I know the items in this list are not direct comparisons. […]

Lubrication: Dry vs Wet – Oil vs Grease


grease gun

One thing that is often looked is lubrication (lube). Changing your lubrication and selecting the proper type can dramatically modify the performance of your system. This change of lubrication was one of the primary reasons MSL was delayed from launching to Mars. Improper lubrication can cause your mechanical parts to wear out and fail. It […]

Incremental Encoder Selection


quadrature encoder

Hi all Just a quick post on incremental encoders. Incremental encoders are good for speed control and can be used for position control when we have a homing routine to get absolute position, or the system is constrained to less than one rotation. One way an incremental encoder can also be an absolute encoder is […]

Wheel & Grouser Design


LRV Wheel

For many robots the wheels are an afterthought however they are essential for letting the robot drive around. Another thing that is often neglected is choosing the proper grousers for your wheel. Most of the design parameters for wheels and grousers are based on experience, intuition (which may or may not be correct) and qualitative […]

Selecting and Sizing Your Motor (and gear boxes)


motor planetary and harmonic gears

Hi all Selecting a motor is a critical task when designing a robot. In a prior post we discussed the different types of motors and feedback options as well as how to control those motors. In this post we will focus on how to size your motor and select the proper gearing. In the main […]

Mechanical Tolerancing


thermal design

Hi all I do not have much to say here except I have seen many cases where tolerancing was wrong in mechanical parts. A general rule is that if you need to assemble parts with a hammer since you can not slide them in your self, it is not correctly toleranced and can cause problems […]

Motors and Feedback (encoders)


brushless motor

Hi all There are many types of motors and feedback methods to choose from. Which do you need? Keep reading to find out more about selecting your motor stackup. Since most field robots are DC powered I am skipping the many types of AC motors that are out there. In addition to this post you […]