Sailing Bright Eternity — Gregory Benford

The final chapter of humanity's future has begun. And three men hold the key to survival. As the fierce, artificially intelligent mechs pursue their savage and unstoppable destruction of the human race, it soon becomes apparent that these three men--three generations in a family of voyagers--are their targets. Toby Bishop, his father, Killeen Bishop, and his long-dead grandfather each carry a piece of the lethal secret that can destroy their relentless pursuers. There's only one problem: they have no idea they possess the only weapon that can save humanity.