In　this　study,　a　novel　free　piston　expander　coupling　with　a　linear　generator　prototype　is　presented　to　recover　exhaust　waste　heat　efficiently　from　vehicle　engine.　The　free　piston　linear　generator　(FPLG)　can　be　used　in　a　small-scale　organic　Rankine　cycle　(ORC)　system　and　can　directly　convert　the　thermodynamic　energy　of　working　fluid　into　electricity.　The　effects　of　intake　pressure,　operation　frequency　as　well　as　external　load　resistance　on　operation　characteristics　and　output　performance　are　discussed.　The　results　show　that　the　piston　displacement　profile　is　similar　to　a　sinusoidal　wave.　The　piston　amplitude　increases　significantly　with　the　increase　of　the　intake　pressure.　It　is　observed　that　the　increase　in　the　operation　frequency　brings　about　the　decrease　in　both　piston　amplitude　and　motion　symmetry.　In　addition,　the　peak　piston　velocity　and　power　output　show　nearly　linear　relation　with　the　intake　pressure,　which　indicates　that　the　power　output　is　sensitive　to　the　piston　velocity.　When　the　operation　frequency　is　1.0　Hz　and　the　external　load　resistance　is　20　Omega,　the　maximum　peak　velocity　is　about　0.69　m/s　and　the　highest　power　output　96　W　is　obtained.　The　conversion　efficiency　of　the　FPLG　increases　with　the　increase　of　the　intake　pressure.　But　the　conversion　efficiency　increases　slightly　when　the　intake　pressure　is　higher　than　2.2　bar.　When　the　operation　frequency　is　2.0　Hz,　energy　conversion　efficiency　of　the　FPLG　can　reach　up　to　45.82%　with　an　intake　pressure　of　2.6　bar.　(C)　2017　Elsevier　Ltd.　All　rights　reserved.