Problem unidentified in project

[Siddhat]

Hey everyone. I have been working on a project namely, "Obstacle Avoiding Robot". The concept is to avoid obstacles and move left or right depending upon the obstacles on right or left of the robot respectively as the name suggests. IR module is used to sense the obstacles. The logic for the task was made using K-map and the circuit seem to worked fine in software until the hardware assembly part was in turn. When the circuit was assembled the motors did not rotate with constant speed but rather rotated not as desired. I could not find out the problem. Plus I was told to use a transistor to drive the motors with constant speed to solve the problem. But I could not figure out how to use the transistor to do so as the motor driver IC has two logic outputs.
The circuit schematic is attached.

[Benta]

You can throw R1 and Q1 away to start.
Apart from that, it's impossible to say. The L293 is real simple, so it's up to your drive system to resolve this, and we don't see that.

[OM222O]

that part allows you to drive 1A through the motors so it shouldn't be an issue ... you need to check your input signals and connections.