Suspension Systems: Shocks, Springs, & Dampers

Watch a Baja Trophy Truck hit a 3-foot bump at 100mph. The body of the truck stays flat. The wheels explode upwards and downwards. It is a violent display of Energy Absorption. A suspension system has two jobs:

1. Comfort: Stop the driver from breaking their spine.
2. Traction: Keep the tire touching the dirt. (A tire in the air creates 0 force).

The Spring (Storage)

The Spring supports the weight of the vehicle. It stores energy.

• Hooke’s Law: $$F = -kx$$.
• The more you squeeze it ($$x$$), the harder it pushes back ($$F$$).
• In robotics, we sometimes stick springs on our wheels to traverse obstacles (like plastic pipes on the field).

The Shock Absorber (Dissipation)

If you only had springs, your car would be a Pogo Stick. You would hit a bump and bounce forever. Enter the Damper (Shock Absorber). Inside the shock is a piston pushing through thick oil.

• Physics: Pushing oil through a tiny hole creates Friction.
• Result: Friction turns Kinetic Energy (Bouncing) into Heat. It kills the bounce instantly. Ideally, you hit a bump, the suspension compresses, expands once, and stops. This is Critical Damping.

Why Robots (Usually) Don’t Have Shocks

FTC fields are flat foam tiles. We don’t need shocks. However, we use the concept of Compliance.

• Flexures: We 3D print plastic mounts that are designed to bend slightly.
• Squishy Wheels: Our Mecanum wheels have rubber rollers that act like micro-suspension.
• Intake Shocks: When a heavy game piece hits our intake, we often mount the intake on a spring-loaded hinge. It absorbs the kinetic energy of the impact so the plastic doesn’t shatter.

Active Suspension

Modern supercars use “Magnetic Ride Control.” They change the thickness of the oil instantly using magnets to become stiff for racing or soft for cruising. In robotics, we use Active Balancing. If our robot is carrying a heavy tower and starts to tip when we stop, we use software to “feather” the deceleration, effectively acting as an electronic shock absorber to smooth out the forces.