Here is another Arduino robot designed to teach students coding and robotics concepts. The Scorpion is based on Arduino. It has omnidirectional wheels and uses ultrasonic sensors and a rear-facing TOF sensor for navigation. It also has a gripper.
Each wheel has a wheel encoder built-in. This robot has a total of 3 ultrasonic sensors. The gripper rotates 180 degrees. This platform is expandable. You can connect it to more advanced sensors and single-board computers like Raspberry Pi.