You could say that motion control systems manufacturer Parker Hannifin (NYSE:PH) exemplifies Newton's first law of inertia: An object in motion stays in motion until acted upon by another force. It seems that Parker Hannifin's business is moving ahead steadily these days.

The maker of things that move materials, controls, machines, vehicles, and equipment during manufacturing reported impressive second-quarter results, with revenues and earnings growing by double-digit rates.

The industrial segment was the primary driver. It accounts for three-quarters of the company's revenues, and it was boosted by the international division, whose 36% growth led to operating income of $121 million, an increase of 79% over last year. The North American division paled by comparison, with its 2.8% increase. So strong were the international unit's results that they now account for nearly 50% of the industrial segment's revenues, and more than one-third of total revenues. Margins, however, remain the best in North America, though the gap has narrowed significantly.

The aerospace segment, which provides hydraulic, fuel, and pneumatic systems to commercial, military, and aviation customers, also made a large contribution, with revenues rising 16% to $402 million. Both it and the international industrial segment account for more than half of Parker Hannifin's revenues, giving the company a far more diversified base than it once had.

Considering the underlying broad strength of the company's operations, it's surprising to see the cheap valuation the market has attached to the stock, which carries a 13 times earnings multiple. While rivals Eaton (NYSE:ETN) and Crane (NYSE:CR) have slightly lower valuations, United Technologies (NYSE:UTX), Curtiss-Wright (NYSE:CW), Donaldson (NYSE:DCI), and Moog (NYSE:MOG-A) all command multiples about one-and-a-half times greater. The market is giving investors a discount on a company with a growth rate over the next five years that's at least equal to if not surpassing the competition.

With a run rate in owner earnings in excess of $872 million, coupled with a conservative 10% growth rate, I can calculate a quick value of the company three years out at more than $1.8 billion, or nearly twice its current market valuation. While there's another saying that what goes up must come down, for the time being, Parker Hannifin is on the move.

For related Foolish articles:

Want some new stock ideas? Learn more about what Motley Fool CAPS players think of the company you're interested in -- or any of 3,500 rated stocks.

Fool contributor Rich Duprey does not own any of the stocks mentioned in this article. You can see his holdings here. The Motley Fool has a disclosure policy.