A holonomic omnidirectional mobile robot with active dual-wheel caster assemblies is proposed as a robotic transport vehicle. With concern to the existence of sudden acceleration and other dynamical effects during maneuver, the tip-over instability monitoring is very important to prevent any unexpected injuries and property damage. This work presents the preventive method of the tip-over occurrence by estimating the tipping direction and stability metrics. The dynamical model of the omnidirectional mobile robot is derived to estimate the net force from the supporting reaction force at each wheel which is caused by the inertial and external forces. The direction of tipping and the stability metric is estimated using Force-angle Stability Measure (FASM). The performance of the tip-over prediction for an omnidirectional mobile robot with active dual-wheel assemblies is shown by the conducted simulations.